The Gay Triangle: The Romance of the First Air Adventurers by Le Queux, William

The Gay Triangle The Romance of the First Air Adventurers. By William Le Queux Published by Jarrolds, Lonodn.

The Gay Triangle, by William Le Queux.

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________________________________________________________________________ THE GAY TRIANGLE, BY WILLIAM LE QUEUX.

CHAPTER ONE.

THE MYSTERY OF RASPUTIN'S JEWELS.

From a derelict shed adjoining a lonely road which stretched for miles across the Norfolk fens, a strange shape slid silently into the night mist. It was a motor-car of an unfamiliar design. The body, of gleaming aluminium, was of unusual width, and was lifted high above the delicate chassis and spidery bicycle wheels that seemed almost too fragile to bear the weight of an engine.

Noiselessly the strange car backed out of the shed. There was no familiar _teuf-teuf_ of the motor-engine; so silent was the car that it might have been driven by electricity, save that the air was filled with the reek of petrol.

Swinging round on the grass of the meadow, the car headed for the gateway, turned into the road, and sped along silently for a few miles.

It halted at length at a point where the narrow roadway widened somewhat and ran along an elevated embankment evidently constructed to raise the road above flood-level.

As the car came to rest, two leather-helmeted figures descended from the tiny cockpit in the body of it. One was a slim young fellow of twenty-five or twenty-six; the other, despite the clinging motor costume, showed feminine grace in every movement. It was a young girl, evidently in the early twenties.

The two set busily to work, and in a few minutes their strange car had undergone a wonderful transformation.

From each side shot out long twin telescopic rods. These, swiftly joined together by rapidly unrolled strips of fabric, soon resolved themselves into the wings of a tiny monoplane. From a cleverly hidden trap-door in the front of the car, appeared an extending shaft bearing a small propeller, whose twin blades, hinged so as to fold alongside the shaft when not in use, were quickly spread out and locked into position. A network of wire stays running from the wings to the fuselage of the car were speedily hooked up and drawn taut.

Then the two mysterious figures climbed again into the transformed car. There was a low, deep hum as the propellers began to revolve, the monoplane shot forward a few yards along the road, then lifted noiselessly, and, graceful and silent as a night-bird, vanished into the shrouding mist.

The adventures of the Gay Triangle had begun!

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Dick Manton, lounging idly in the Assembly Hall of the little town of Fenways, in the centre of the Norfolk Broads, watched with eyes half critical and half amused the throng of dancers circling gaily to the strains of three violins and a tinkling piano which did duty for an orchestra when the youth of Fenways amused itself with a dance.

Dick was wholly and entirely a product of the war. The lithe, slim body, hatchet face, and keen, resolute eyes stamped him from head to foot with the unmistakable _cachet_ of the airman. He smiled, as he watched the dancers, in acknowledgment of the gay greeting flung to him by a score of laughing girls who, with the joy of youth, were giving themselves unreservedly to the pleasures of the fox-trot.

Dick was a general favourite, and more than one pretty girl in the room would have been only too glad to arouse something more than a passing interest in the young airman, whose dare-devil exploits above the German lines in France had brought him the Flying Cross, whose brilliant career had been cut short by a bullet wound, received in a "dog-fight" above Bethune, which had rendered him unfit for the continual hardships of active service. He had been offered a "cushy" job in acknowledgment of his services. But Dick could not bear the idea of being "in the show" and yet not of it, and had accepted his discharge with what philosophy he could muster.

His chief asset was his amazing knowledge of motor-engines. They had been his one absorbing craze. While in the Army he had studied intently every type of engine to which he could gain access; he had read every book on the subject upon which he could lay his hands, and even among the expert pilots of the Air Force he was acknowledged as a master of engine craft.

It was this knowledge of engines which had sent Dick into the motor business. He knew, of course, that he could have obtained a good post with one of the big companies had he chosen to stay in London. But his nerves were still tingling from the stress of war, and he was still weak from the after effects of his wounds. So, for the sake of peace and fresh air, he had invested a part of his capital in a small motor business at Fenways. If he was not making a fortune he was at least living, and the keen Norfolk air was rapidly bringing him back to health.

At times the longing for the old life, the rash and whirl of the city, came upon him with almost overwhelming force.

Suddenly a cameo of his days in France leapt into his mental vision. He found himself once again staring, as in a mirror, at the slim figure of a half-fainting French girl stealing through the dusk towards the British lines. A crackling volley of shots from the Boche lines followed her, but by some miracle she came on unhurt. Dick had been sent up to the front to supervise the removal of a German plane of a new pattern which had crashed just behind the trenches and had wandered into the front line (where, of course, he had no business!), and it was he who caught the exhausted girl in his arms as she dropped into the British trench.

He had often wondered since what had become of Yvette Pasquet. She had stayed on in the little town where Dick's squadron was stationed, and they had become good friends. Dick had thus learnt something of her tragic history.

An Alsatian, French to the finger-tips, Yvette had lived in London for some years and spoke English well. But she had seen her father and mother shot down by the Germans on the threshold of their home, and she herself had only been preserved from a worse fate by a young German officer, who had risked his life to save her from his drink-maddened soldiers. Sweet and gentle in all other respects, Yvette Pasquet was a merciless fiend where Germans were concerned; her hatred of them reached a passion of intensity which dominated every other emotion.

How she had managed to get through the German lines she never quite remembered. Her father had been well-to-do, and before her escape after the final tragedy, Yvette had managed to secure the scrip and shares which represented the bulk of his fortune, and had brought them across with her safely concealed under her clothing.

From that time forward she had been the brain of a remarkable organisation which had devoted itself to smuggling from the occupied regions into France gold, jewellery, and securities, which had been hidden from the prying eyes of the Hun.

After his wound Dick had lost sight of her. For many months he had lain dangerously ill, and when he had recovered sufficiently to write, Yvette had disappeared.

Dick's reverie was broken at length by a light touch on his arm. "A penny for your thoughts!" said a soft voice at his elbow.

Dick came to earth with a jerk. The voice was that of Yvette herself! And when he turned he found her standing beside him, smiling into his face with the light of sheer mischief dancing in her brilliant eyes. With her was a tall young Frenchman, obviously her brother.

"Yvette!" Dick gasped in sheer amazement. "What on earth brings you here?"

"I came to look for you, my friend," was the quaint but sufficiently startling reply in excellent English. "But let me present my brother. Jules--this is Mr Manton."

Dick, his head in a whirl, mechanically acknowledged the introduction. Yvette had come to look for him! What could it mean?

"We came down from London this evening," Yvette explained, "and are staying at the `George.' We soon found your rooms, and hearing you were here decided to give you a surprise."

"You have certainly succeeded," Dick rejoined. "But how on earth did you learn I was in Fenways?"

"Well," said Yvette, "it's no mystery. I happened to meet Vincent quite by accident in Paris, and he told me where you were." Vincent was an old flying colleague, and one of the very few people with whom Dick had cared to keep in touch.

"I have tried several times to find you," went on the girl, "but even your own War Office didn't seem to know what had become of you after you left the Army, and my letters were returned to me."

Then her manner changed.

"Dick," she said seriously, "I came down to see you on business-- important business. I can't explain here. I want you to come back to Town with us in the morning. My brother and I have a proposition to put before you. We want your help. Will you come?"

Wonderingly, Dick consented.

"Yes," he said, "I shall be glad. My assistant can quite well look after things here while I am away."

"Very well," said Yvette, with a look of relief which did not escape Dick, "that's settled. Now let us enjoy ourselves."

Dick spent a sleepless night, crowded with old memories which kept him wide awake. Next morning he found himself with his two companions in the train for London. Arriving at Liverpool Street, they took a taxi and were soon comfortably ensconced in a private room at a small but exclusive West End hotel.

It was not until after lunch that Yvette opened a conversation that was destined to exercise a powerful influence on Dick Manton's career.

"Now, Dick,"--she called him "Deek"--"before I say anything I must make it a condition that under no circumstances will you ever mention what passes between us. I know I can trust you implicitly. I am going to make you an offer which you are absolutely free either to accept or refuse. It will surprise you, and you are entitled to a full explanation. But in case you refuse, not a word of our conversation must ever pass your lips under any circumstances whatever. Do you agree?"

"Of course I do," replied Dick, wondering what was coming.

"Very well," laughed Yvette, "now I can tell you everything."

"You will remember," she went on, "what I was doing in France--smuggling money and valuables out of the reach of the Germans. Well, I am doing the same thing still, but on a different scale and by different methods. I dare say you know that there is an enormous amount of smuggling into England; the heavy import duties have made it a very profitable game. What you probably don't know is that it is mostly carried on by Germans. There is a regular organisation at work, clever, secret, and highly efficient. But the chain, like every chain, has a weak link, and I happen to have found it. The head of the whole undertaking is Otto Kranzler, of Frankfort. You will remember him. He was the commandant responsible for the murder of my father and mother."

"I remember!" Dick exclaimed.

"At the very moment Kranzler is in Paris, looking for an opportunity to get into England with a wonderful collection of jewels, which formed a part of those given to the mock-monk Rasputin by the late Czarina of Russia and some of his wealthy female admirers. Now, Dick, I want those jewels, and I am going to have them?"

"But how?" queried Dick.

"Kranzler is in a serious difficulty. So far as I can make out the jewels were brought into Germany by a Bolshevik agent for disposal, of course, against the German law. Rasputin's jewels were liable to confiscation, and by some means the German Secret Police got wind of the affair. Kranzler, however, was too quick for them, and slipped over the frontier into France in the nick of time. Now he is in a quandary.

"Under French law he has so far committed no offence, and cannot be arrested. But if he attempts either to deal in the jewels or to export them he will find himself in trouble. The French police are wide-awake--of course, they got a tip from the Germans--and are watching him as a cat watches a mouse.

"So there he is," she went on, "planted in an hotel with jewels worth at least fifty thousand pounds, and unable to move! His one chance is to get the jewels away by a messenger. He is clever and may succeed, but I don't think he will. He has already tried but without success.

"I have a plan. I think I can get the jewels out of the hotel. But they must be brought to England, and there is the difficulty. When Kranzler loses them he can't make any formal complaint, but he will certainly get out of France as speedily as possible; that will give the game away, and the watch on the boats will be keener than ever. I dare not risk sending them by a messenger. An aeroplane is the only chance. And I want you to fly that aeroplane!"

Dick coloured painfully.

"But, my dear Yvette," he stammered, "you don't mean to say you intend--?"

"To steal the jewels?" Yvette completed the sentence.

"Yes," Dick admitted, horribly embarrassed. He found it impossible to associate Yvette with what appeared to him a piece of cold-blooded larceny.

"I quite expected you to say that, Dick," Yvette replied. "And perhaps I should have thought less of you if you had said anything else. But surely you don't take me for a common thief?" Without waiting for Dick's reply, she went on: "Now, try to look at this affair through our French eyes for a moment. I'm going to have those jewels--at least, I'm going to try. Who am I hurting? A German who robbed me of my father and mother! Would any Frenchman or Frenchwoman hesitate a moment? He is a thief and a murderer! Whom am I benefiting? Myself? Not for a moment; I wouldn't touch a penny of the money. If I bring this off--and I think I shall--there will be at least a million francs to help on the restoration of the devastated regions of France. Now, Dick, you helped France once. Won't you do it again? I must have some one I can trust, and I know no one but yourself. It will be great sport to beat the police of two countries," she added with a laugh.

Dick's imagination caught fire. It was impossible to resist Yvette's appeal. He was more weary than he knew of his humdrum life in Norfolk, and here was an adventure after his own heart. His mind was swiftly made up.

"I'm on, Yvette!" he said shortly.

To his amazement, the girl burst into a sudden passion of tears.

"On? Dick--if you could only realise what it means to me!" she sobbed. "I have been all through the smashed-up parts of France--everything, even our churches, is smashed and broken and defiled. The poor people are working desperately to restore their old homes, and they only want help to be happy again. But France has no money, and Germany won't pay--as every one foresaw except your British statesmen. Do you think I am likely to hesitate to rob a German thief when it means happiness for hundreds of French men and women and children?"

He tried clumsily to comfort her, and at length she grew more calm.

"There is no time to be lost," she declared. "We must get over to Paris to-night. I have lately learnt to fly, and my aeroplane is hidden a few miles from Paris. The real problem is to get hold of the jewels and bring them safely out of the hotel. Then the aeroplane can start at once."

"But what about Lympne?" Dick asked. "You know all aeroplanes entering England from the Continent must land at Lympne for identification and customs examination. And the jewels would certainly be found."

"You must not land at Lympne," Yvette declared positively. "You will have to get in unobserved and land somewhere away from any aerodrome. You can abandon the aeroplane; that won't matter if you get through safely."

"And leave it to be identified in a few hours' time by the engine marks?" asked Dick. "No, Yvette, that won't do. And besides," he went on, "there wouldn't be the slightest chance of getting through. The new wireless direction-finders would give me away long before I could even reach the coast, and the Air Police would do the rest. I should simply be shadowed till I landed--or even shot down if I refused to land! Four smuggling planes were picked up last week by the new wireless-detectors, and every one was captured."

"Then I don't know what I shall do," Yvette replied blankly. "I thought you would surely be able to slip over at night."

Then Dick, even against his better judgment, which warned him he was taking on a foolhardy enterprise, sprang his great surprise.

"Well," he said, "perhaps I can help you, after all. You know, in Fenways I'm supposed to be only a motor-dealer. Really, I have been working for over two years quite secretly on a combination of aeroplane and motor-car, and now I think I have got it about perfect. You can change the motor-car to a little monoplane in less than half an hour. The wing struts telescope back into the body, so does the propeller-shaft, and the blades fold back along the shaft."

"Have you really?" she gasped eagerly.

"Yes. Best of all, I've got an absolute silencer on the exhaust; I've run the engine at top speed on the ground and found I could not hear it a hundred yards away. So far I have only made one or two flights, but they were quite successful. It seats two in little cockpits placed one on each side of the centre line where the propeller shaft runs. Why shouldn't we try to fly her over tonight? I feel pretty sure we could do it at ten thousand feet without the direction-finders knowing anything about us."

"Excellent!" cried the girl.

"The great disadvantage is that I can't get any speed to speak of on the ground. I have had to make everything very light, of course, and I fancy about twenty miles an hour, unless the roads were exceptionally good, would be our limit. We should have no chance of getting away if we were chased on the ground--or in the air, for that matter--if we were spotted. We might fly over to-night and chance getting caught. Of course, I have my pilot's certificate, and if we were caught I could easily explain that I was making a night flight and my compass had gone wrong. It wouldn't be a very serious matter the first time as, of course, we should have nothing contraband. If we got over safely we could take the chance of coming back loaded."

Yvette had become suddenly radiant.

"Why, Dick!" she cried, "that's the very thing. We simply can't be caught. And when we land anywhere we can be ordinary motorists. It's wonderful--wonderful!"

"Don't be too sure," replied Dick grimly. "The Air Police are pretty wide awake. However, it's worth trying. Now, shall we go to-night? There's a train from Liverpool Street at six-twenty. We shall get down to Fenways by nine. We shall have five miles to walk to the shed where I keep the machine--of course, we daren't drive out--and we must manage to reach Paris about dawn. If we are too early I cannot land in the dark, and if we are late people will be about and we shall run the risk of being spotted."

Yvette promptly produced a small but beautifully clear contour map.

"There's your landing-place," she said, pointing to a large clearing surrounded by thick woods. "It's about fifteen miles from Paris, and my own aeroplane is pushed in under the edge of the trees. It is quite a lonely spot in the forest a little to the north of Triel. Of late years the forest has been very much neglected and very few people go there. An old farmer, who lives quite alone, grazes a few sheep in the clearing, and I have, of course, had to arrange with him about my machine. He thinks I am an amateur flyer, and I have told him I am making some secret experiments and paid him to keep quiet. I flew the machine there myself when I bought it from the Francois Freres, of Bordeaux. Of course, I had my papers all in order when I bought it."

"All right; that will do well enough," said Dick. "We will go over to-night. Jules can go by the boat train."

A few hours later Dick and Yvette were standing in the shed beside the strange motor-car, Dick rapidly explaining the system of converting the machine into a monoplane.

"We must get off the ground as quickly as possible," he said. "People go to bed early in these parts, but there is always a chance of some one being about, and I don't want to be caught while we are making the change."

At a suitable spot on the road, the change was made. It occupied Dick, with Yvette's skilful help, just twenty minutes.

"We can do it in fifteen," he declared, "when you are thoroughly accustomed to it."

As a matter of fact they did it in less on one memorable occasion some weeks later when their pursuers were hot on their heels.

Soon they were speeding swiftly southwards. Dick had set the monoplane on a steep, upward slant, aiming to reach ten thousand feet before he drew abreast of London. Thanks to the clinging mist, they were soon utterly out of sight from below, and Dick had to steer by compass until they sighted thirty miles ahead, and slightly to their right, the great twin beams of light which marked the huge aerodrome at Croydon.

Then Dick veered to the south-east, flying straight for Lympne and the French coast. After all, he argued, the bold course was the best. No one would expect an aeroplane on an illicit errand to venture right above the head-quarters of the Air Police, and should any machine be about on lawful business the noise of their engines would prevent the detectors picking up the throbbing whirr of the propeller, which, of course, could not be absolutely silenced.

Fortune favoured them. As they drew nearer to Lympne, swinging in from the slightly easterly course he had set, Dick caught sight of the navigation lights of the big mail aeroplane heading from London to Paris. His own machine, bearing, of course, no lights, was far above the stranger, the thunder of whose big engines came clearly up to them. A couple of red flares from the big plane signalled her code to the aerodrome, the searchlight blinked an acknowledgment, and the mail plane tore swiftly onward. Dick could not match its hurtling speed, but he followed along its track, confident that he would now be undetected.

They swept silently above the brilliantly lighted aerodrome, then across the Channel, and just as dawn was breaking detected the Triel forest, and dropped lightly to earth almost alongside Yvette's machine. By eight o'clock the machine, now a motor-car, was safely locked up in a disused stable in the Montmartre quarter of Paris, and Dick, Jules, and Yvette were soon in deep consultation.

That evening, just as dusk was falling, a half-drunken coachman sprawled lazily on a bench set against a wall in the deep courtyard of the "Baton d'Or," a quiet hotel located in aback street in the market quarter of Paris. By his side was a bottle of _vin blanc_. Before him, harnessed to a dilapidated carriage, stood his horse, a dejected-looking animal enough.

Directly over his head, at a window of a room on the third floor, two men stood talking. One of them was Otto Kranzler.

Two rooms away, on the same floor, a curious little drama was being enacted.

Lounging on a sofa near the door was Dick Manton. Yvette, on a chair drawn near the window, faced him.

Yvette rang the bell, and the two were talking when a chambermaid appeared.

"Coffee and cognac for two," Yvette ordered.

A few minutes later the girl reappeared. She crossed the room with a tray and set it on the table in front of Yvette.

As the maid turned Dick's arm was slipped round her, and a chloroformed pad was pressed swiftly over her face. Taken utterly by surprise, the girl was too firmly held to do more than struggle convulsively, and in a few moments, as the drug took effect, she lay a limp heap in Dick's arms.

Snatching from a valise a chambermaid's costume and cap, Yvette swiftly transformed herself into a replica of the unconscious girl. Then picking up the tray and its contents she silently left the room, having poured a few drops of colourless liquid into each of the glasses of brandy.

Kranzler was evidently in a bad temper.

"I tell you," he said to his companion, "there _must_ be a way out. That infernal--"

There was a knock at the door, and a chambermaid entered with coffee and liqueurs. It was Yvette!

"Would the messieurs require anything further?" she asked as she set down the tray.

"No, that's all for to-night," said Kranzler in a surly tone, as he picked up the brandy and drained it with obvious relish. His companion followed suit.

Dick was sitting beside the unconscious girl as Yvette re-entered the room.

"She's quite all right," he said, as he watched her narrowly for signs of returning consciousness, "but I must give her a little more just as we are leaving. How did you get on?"

"Splendidly," said Yvette; "they noticed nothing, and I saw them both drink the brandy as I left the room."

Ten minutes later Yvette re-entered Kranzler's room. The two men had collapsed into chairs. Both were sleeping heavily.

Without losing a second Yvette tore open Kranzler's waistcoat and passed her hand rapidly over his body. A moment later she had slit open the unconscious man's shirt, and from a belt of webbing which ran round his shoulders cut away a flat leather pouch.

From her pocket she took a reel of strong black thread. To one end of this she fastened the pouch, and, crouching by the open window, pushed the pouch over the sill and swiftly lowered it into the darkness.

A moment later came a sort of tug at the line, the thread snapped, and Yvette let the end fall. Then, with a glance at her drugged victims, she snatched up the tray and returned with it to her own room.

Lying on the sofa, the chambermaid stirred uneasily. She was evidently recovering. While Yvette swiftly discarded her disguise Dick again pressed the chloroform to the girl's face.

A few moments later "Mr and Mrs Wilson, of London," were being escorted by the hotel porter to a waiting taxi-cab.

They never returned.

In the semi-darkness of the courtyard the drunken coachman had stiffened and leant back against the wall as a small, dark object lightly touched his shoulder. His arm, twisted behind him, felt for and found a slender thread. Held against the wall behind him was the flat leather pouch which Yvette had lowered. A moment later it was transferred to a capacious pocket, and the coachman, staggering uncertainly to his horse, mounted the carriage and drove noisily out of the yard. No one paid the slightest attention to him; no one realised that that uncouth exterior concealed the slim form of Jules Pasquet, his nerves quivering with excitement at the success of the Gay Triangle's first daring _coup_.

An hour later the Paris police took charge of an old horse found aimlessly dragging an empty carriage along one of the boulevards. About the same time, from a forest clearing fifteen miles away from Paris, a tiny monoplane rose silently into the air and sped away in the direction of the French coast.

Kranzler left Paris the following day and returned to Germany. He was strictly searched at the frontier, of course without result, and the puzzled French police never solved the problem of how, as they thought, he had beaten them. He had not dared to complain. "Mr and Mrs Wilson" were never even suspected, for by a strange coincidence some articles of jewellery were stolen from another room that same night, and when the drugged chambermaid told her story it was assumed that the Wilsons were hotel thieves of the ordinary type.

A month later the _Petit Parisien_ announced in black type with a flaring headline:

"An anonymous gift of one million francs has been received by the French Government, to be devoted to the relief of the devastated regions of France."

CHAPTER TWO.

A RACE FOR A THRONE.

Paris, keenly sensitive to political vibrations which left less emotional centres relatively unmoved, was rippling with excitement.

The death of the aged King John of Galdavia had been followed by the sudden appearance of a second claimant to the stormy throne of the latter principality in the Middle East, and the stormy petrels of politics, to whom international political complications are as the breath of life, had scented trouble from afar, and were flocking to the gay city. For the moment, however, the rest of the world seemed to take but little interest in the new problem. It was generally felt that the succession to the Throne of Galdavia was a matter for the Galdavians alone, and only a few long-sighted individuals perceived the small cloud, "no bigger than a man's hand," which threatened to darken the entire political firmament.

Back in his quiet Norfolk home, Dick Manton had dropped into a state of profound dejection. The adventure of the Russian Jewels, with its wild plunge into the thrills of the old life, had awakened an irrepressible desire for action and movement which had lain dormant while his shattered health was being slowly re-established.

Now, fully recovered, and in the perfection of physical condition, he could only contemplate with distaste and aversion continued existence in the humdrum surroundings of East Anglia.

But what was he to do? Like thousands of others he felt that the ordered life of civilisation, with every daily action laid out according to plan, was for him impossible. His was essentially one of the restless spirits, stirred into life by the war, which craved action, difficulty, and even danger. Moreover his growing affection for Yvette troubled him.

Yvette had been delicately brought up. She was accustomed to luxury, and Dick could only realise that his present prospects were such that, even if he were sure she cared for him, a marriage between them must entail such sacrifice on her part as he could not contemplate with equanimity.

But, though dull, he had not been idle. The brilliant initial test of the new motor-plane, which he had fancifully christened "The Mohawk" had stirred his ambition, and every moment he could snatch from business had been devoted to thinking out and applying improvements. Some of these had been of real importance, and the machine had gained substantially in strength and lifting power, as well as in speed both on the ground and in the air. He was also making experiments in gliding.

For some months he had heard little of Yvette. A few brief notes had told him she was well. But that was all, and he felt a little hurt. He never dreamed that Yvette's feelings were singularly like his own; that she, too, was the prey of emotions which sometimes alarmed her. They were, in fact, kept apart by Dick's shyness and poverty, and by the French girl's profound pride and reserve.

Matters were in this stage when Dick, to his great surprise, received a brief telegram from Yvette.

"Can you come to Paris? very urgent--Yvette," the message ran.

Dick left at once and next evening found him with Yvette and Jules at a small hotel near the Gare du Nord. After a cordial greeting Yvette, as usual, plunged direct into the business in hand.

"Now, Dick," she said, "our last adventure was quite a success. Are you good for something more exciting and decidedly more dangerous? Or," she added mischievously, "is Norfolk and the motor business exciting and dangerous enough for you?"

Dick laughed.

"To tell the truth," he replied, smiling, "I'm about fed up with both of them. You can count me in on anything short of murder."

"I hope it won't come to that," was Yvette's rejoinder, "but I admit you may find your automatic pistol useful, perhaps indispensable. But let me explain. You English don't take much interest in foreign politics, and perhaps you haven't--in Norfolk--paid much attention to Galdavia."

"I read that King John has died," Dick rejoined, "but I didn't suppose it made much difference."

"Just as I expected!" said Yvette, laughing. "Well, it does; it makes quite a lot of difference as it happens. Of course it ought not to. In the ordinary way Milenko, the son of King John, should succeed peacefully enough. But he has done some foolish things, and he is not too popular. There is a strong party in Galdavia which professes to object to the manner in which John was called to the throne. You know, of course, how it happened; he was summoned after his predecessor, King Boris, was killed by a bomb. Legally, of course, Milenko's claim is unchallengeable. But legality doesn't count for too much in Galdavian politics, and a second claimant to the throne has appeared in the person of Prince Michael Ostrovitch, whose title lies in the fact that he is descended from a brother of Boris's grandfather. He was only a boy when John was chosen, and in any case he would have had no possible chance of election, for Galdavian opinion then was overwhelmingly in favour of John. But there has been a change. The change would not be enough to cause uneasiness, but for the appearance of another and very sinister influence," and she paused.

"We are convinced that Germany, for very obvious motives, is backing Prince Ostrovitch," she went on. "The scheme is being very skilfully worked, and so far we have failed entirely to secure positive proof. If we could do so the plot would be at an end, for France and Great Britain, and perhaps even America would intervene at once. They would never allow a German puppet to ascend the throne of Galdavia. But they would not interfere with a _fait accompli_, especially if Ostrovitch's election were so stage-managed as to give it the appearance of a popular movement."

"I quite see the point," Manton said, much interested.

"Now we have found out this much," she went on. "Jules and I have been working at the case for some weeks, and we have both been to Langengrad, the capital. The secret is there. Bausch and Horst,"--she named two well-known agents of the German Foreign Office--"are both there, disguised and under assumed names. We believe that a formal agreement is being prepared between the Ostrovitch Party and Germany. Now, neither the Germans nor the Ostrovitch Party fully trust one another, and each will seek to safeguard itself by documents which in the event of treachery by either side would mean certain ruin. I am convinced that such a document either exists or is being drawn up, and we must get hold of it if the peace of Europe is to be kept. Now," she added slowly, "I want you to come with me to Langengrad and get it!"

Dick sat silent for a moment.

"I want to ask one or two questions," he said at length. "Do you mind telling me how you come to be in this?"

"I expected that, of course," replied Yvette. "The answer is simple enough. I have been working for a long time for the French Secret Service."

"And why do you want me?" Dick queried.

Yvette coloured.

"I didn't expect that, Dick," she answered slowly. "I want you first because I know you thoroughly, and secondly because I must have the Mohawk. If you decide to go we shall go in the Mohawk as motorists touring for pleasure. But if we succeed we shall certainly have to leave Langengrad in a desperate hurry, and we should certainly find all the roads blocked. What chance do you think a motor-car, to say nothing of such a conspicuous oddity as the Mohawk, would have of getting all through Austria-Hungary and Germany, even if it got over the Galdavian frontier, when so many people in Galdavia, Austria, and Germany would have the liveliest interest in stopping it? No, we must fly out of Galdavia. We cannot fly in, because our passports must be in order--but we shall have to fly out."

Dick smiled, but made no comment.

"But remember this," the girl said, "if we arouse the slightest suspicion it is a hundred to one we shall never return. The French Foreign Office cannot appear in the matter under any circumstances. If we succeed, it means a big reward; if we fall into Ostrovitch's hands--!" and a shrug of Yvette's shapely shoulders ended the sentence.

"Very well, Yvette," exclaimed Manton. "I'll go with you. There's no one to worry about me, anyhow, and I'm fed up with Norfolk. When do we start?"

"The sooner the better. Is the Mohawk ready?"

"Yes," replied Dick. "I can start half an hour after I get back."

"Then you had better go over by the air express to-morrow morning," replied Yvette, "and fly back to-morrow night. I will meet you at the old place ready to start. You can leave all papers to me."

Then Jules took up the story and for a couple of hours Dick listened carefully to the details of the organisation which Jules and Yvette had set up in Langengrad, and he marvelled greatly at the extent and thoroughness of the work which had been done in so short a time.

A few days later Dick and Yvette, under the names of Monsieur and Mademoiselle Victor, sister and brother, crossed the German frontier in the Mohawk in the guise of tourists motoring through Germany and Austria-Hungary to Galdavia. Their passports, prepared by the French Secret Service and bearing all the necessary _visas_, got them through without the smallest difficulty. Speaking French really well, Dick had no doubt that, outside France at any rate, he could safely pass for a young French officer. Jules had remained behind to carry out his share of the campaign.

Dick drove steadily via Stuttgart and Munich to Salzburg, where he loaded up the Mohawk with all the petrol she could carry for the last stage of the journey. From Salzburg he proposed to fly across the mountains to Klagenfurt, where he hoped to pick up the line of the Drave River and follow it to its confluence with the Danube. From there a brief trip by road would bring them to the borders of Galdavia.

It was a lovely autumn evening when the queer-looking motor-car left the "Bristol Hotel" at Salzburg and slid along the road to Radstadt, the "winter sport" resort. Very soon a sufficiently lonely spot was reached and from a smooth patch of moorland turf the Mohawk rose into the air just as the full moon was rising above the great mountains. The engine was working splendidly and the Mohawk climbing swiftly into the keen air travelled steadily until, just before midnight, Dick and Yvette sighted simultaneously the lake at Klagenfurt and the silvery line of the Drave stretching away to the eastward.

With nearly three hundred miles to fly Dick set the Mohawk on a course parallel to the Drave and slightly to the south of it, and for hour after hour they flew on through the brilliant night. Five thousand feet up, they had no fear of detection and gave themselves up to enjoy the beauty of the glorious panorama unfolded below them.

In less than five hours the Danube was sighted and crossed, and just as dawn was breaking, the Mohawk came to earth a few miles from the little town of Neusatz. Quickly the aeroplane was metamorphosed into a motor-car and the "tourists" ran into Neusatz, the little Danube town, for breakfast and rest. A few hours later they were across the borders of Galdavia and heading for Langengrad, the old capital surmounted by a frowning fortress built by the Turks in the Middle Ages.

Twenty-five miles from the city they halted at a wayside inn.

"This is where we shall meet Fedor," Yvette explained.

It was not until after they had had dinner, a homely meal in the true Galdavian fashion, and it grew dark, that they heard from the roadway three sharp blasts on a motor-horn.

"There he is!" exclaimed the shrewd athletic girl. "Get the car out, Dick!"

The latter hurried to the shed at the rear which served as a garage and when, a few moments later, he drove the Mohawk into the white dusty roadway he found a big touring car drawn up and Yvette talking to a tall, dark-eyed young fellow whom she introduced to Dick as "Count Fedor Ruffo."

Dick gazed at him with quick interest, for he had heard much of a wonderful invention of the Count which was expected to play an important part in their quest. Fedor was a young fellow of quiet demeanour, with the long nervous hands of an artist, a delicately cultured voice and soft dreamy eyes. Dick took him for an Austrian, which he afterwards found to be correct. He had taken a high degree in science at Vienna and had settled in Langengrad as a teacher at the University there.

"Follow the Count's car as closely as possible, Dick," said Yvette. "We want to slip into Langengrad unnoticed, if possible. The fewer people who see the Mohawk the better."

The Count's car moved away almost noiselessly into the darkness. Several times Fedor stopped and listened intently, and once they waited an hour at a point where two roads crossed. Nothing happened, however, and about one o'clock in the morning they reached the outskirts of Langengrad. Here the Count left the main road and slipped into a series of crooked by-streets lit only by the light of the moon. Finally, he turned into the courtyard of an old-fashioned house standing in its own grounds and the Mohawk was speedily backed into a large empty shed, and the door locked.

"Now, Mr Manton," said the Count in fair English, "will you drive Miss Pasquet in my car to the Continental and register there? She knows the way. Rooms have been taken for you. You had better use my car while you are here. In the meantime if we meet in public remember we are strangers. Foreigners here are pretty closely watched."

The Hotel Continental at Langengrad is one of those cosmopolitan caravanserais dear to the heart of the tourist. As usual it was crowded, and even at two o'clock in the morning the cafe was humming with activity. Consequently Dick and Yvette arrived almost unnoticed. Explaining that they had been delayed by a motor breakdown they were soon in their rooms and were sound asleep.

Next morning Yvette took Dick out into the gay pleasant city of boulevards and handsome buildings. He was immensely interested in the brilliant scene, but he realised they were on a desperate mission and took care to fix firmly in his mind the roads they would have to use. It was necessary, of course, to keep up the appearance of being mere gaping sightseers and they went from shop to shop buying a quantity of souvenirs which neither desired in the smallest degree, and arranging for them to be delivered to their hotel.

In the Balkanskaya, one of the principal streets, Yvette paused at last before a jewellers' window which blazed with gems. A moment later, followed by Dick, she slipped into a narrow passage at the side of the shop and turning into a doorway began to mount a flight of stairs which seemingly led to suites of offices in the upper part of the building. On the third floor she halted before a dingy door, and knocked softly.

Instantly the door was opened by Fedor who, inviting them within, shut the door and locked it. "Well, Fedor, what luck?" Yvette asked.

"The best," was the reply. "We have been able to find out exactly the people with whom Bausch and Horst are associating, and where their meetings are being held. You have arrived in the very nick of time. I fancy--indeed, I am almost sure--the agreement will be signed either to-night or to-morrow night. I have overheard most of their talk."

"But how have you managed that?" Dick asked eagerly.

"Miss Pasquet's telephone, of course," said Fedor. "Didn't she tell you about it?" Yvette blushed and laughed.

"You didn't know I was an electrician, did you, Dick?" she said. "Well, you will soon see my little invention at work. But it is nothing to compare with Fedor's."

The good-looking Count talked earnestly for half an hour, acquainting them fully with the work of Yvette's agents in the Galdavian capital, until Dick became amazed at the perfection of the organisation which the alert young French girl had so swiftly created.

"Ostrovitch's Party," Fedor concluded, "usually meet at the house of General Mestich, who, as you know, is the Commander of the Headquarter Troops in Langengrad. He is a wonderfully able man, but is a confirmed gambler and _bon viveur_, and is head over ears in debt. He plays at the Jockey Club each night. There can be no doubt whatever that he has been bought by Germany. His house in the Dalmatinska for a long time has been notorious for its rowdy parties, and as a result it is quite easy for the conspirators to meet there without attracting undue attention. I am certain the Government does not realise how far things have gone yet. There is not a scrap of direct evidence. Mestich is personally very popular, and would in any ordinary matter carry with him a big volume of public opinion. But he dare not, as yet, venture on any direct revolutionary action. His hope is to give his plot some semblance of a popular movement, and he is gradually winning important adherents. If he is given enough time I think he will succeed. But without Bausch and Horst--that is without Germany--the plot must go to pieces. They are finding the money, which is being spent like water."

"This is certainly interesting," Dick exclaimed. "What are your intentions?"

"Well, immediately opposite Mestich's house is an old building which for many years has been used as a store. It belongs to a loyalist friend of ours, and I can use it as I like. From one of the upper windows it is possible to see right into Mestich's little _salon_, where the meetings are held. We will meet there to-night. You must come separately to the alley at the back; we dare not enter by the front. There is a small doorway there, half overgrown by clematis and apparently never used. I will be inside waiting to open the door when you knock."

For the rest of the day Dick and Yvette were careful to behave as ordinary tourists "doing the sights" of Langengrad, the Rathaus, the Museum, and the Opera House, and still buying piles of useless souvenirs. But they were soon to realise that a careful watch was kept on all strangers in Langengrad.

Just as they were finishing dinner that night they were approached by an officious little black-moustached man who sent a waiter to call them aside. When they were in a small smoking-room he made a courteous request for their papers. These were, of course, in order, and Dick had no misgivings on the point. But for some reason the shrewd, sallow-faced official seemed suspicious, and Dick noticed with anxiety that he spoke faultless French.

Would his own, he wondered, pass muster?

"Monsieur speaks French like an Englishman," the police officer suddenly rapped out.

Luckily Dick was prepared.

"Yes," he answered readily, "I was brought up in England. I was at school at Rugby. My friends in our French Air Force nicknamed me `The Englishman.'"

The officer, it appeared, had also been an airman and proceeded to talk interestingly on the subject of aero engines. He was perfectly courteous, but none the less Dick had an uncomfortable suspicion that he was beneath a human microscope. Fortunately the subject was on one which he could not possibly be "stumped" and try as he would the police official found he had met his match.

Dick was intensely interested and amused by his skill and courtesy. None the less the position was most dangerous. He realised fully that-- as was indeed the fact--the officer might be one of Mestich's lieutenants, and unless he could be satisfied their chances of getting away from Langengrad were trifling.

At length he seemed satisfied that Dick was really what he pretended to be, and finally left them with a courteous farewell, having accepted a glass of slivovitza--or plum gin--the liqueur of the Galdavians--and chatted for a time on ordinary topics.

"That man is dangerous, Dick," whispered Yvette when he had gone. "We shall have to be most careful. I wish I knew how much he knows, or suspects."

They were soon to learn how acute this visitor really was!

Shortly after, Dick, smoking an exquisite cigarette such as can only be bought in Langengrad, a dark coat thrown over his evening dress, left the hotel quite openly, but keenly on the alert. He suspected he might be followed, a premonition that was to prove useful.

He strolled idly through the broad Kossowska agog with evening life, gradually working his way towards the rendezvous, and keeping a sharp look out. Soon he picked out the figure of a man who always seemed to be about fifty yards behind him. A few turns through side streets confirmed his suspicions; clearly, he was being "shadowed!"

Dick Manton's brain always worked rapidly in a crisis. Obviously the man must be got rid of. So he speedily formed a plan.

Strolling down the alley behind the old storehouse, Dick marked the exact locality of the clematis-grown doorway, passed it and then turned, so timing his movement that he and his pursuer met exactly outside the door. It was the agent of political police who had interrogated him after dinner!

Further pretence was useless, and Dick came straight to the point.

"To what am I indebted for Monsieur's very polite attentions?" he demanded bluntly.

The stranger shrugged his shoulders insolently.

"Langengrad at night is not too healthy for foreigners," he replied with an obvious sneer, "and of course we feel responsible for--"

He got no further. Dick's clenched fist jerked upward with every ounce of his strength and skill behind it. Taken utterly by surprise the police agent was caught squarely on the point of the jaw and went down like a log.

Dick tapped at the door, which was instantly opened by Fedor, and together they dragged the unconscious officer inside. A moment later he was securely bound, gagged and blindfolded.

Dick was now thoroughly alarmed about Yvette. Would she be followed, and if so, could she win clear?

Here fortune favoured them. Apparently the police official, whatever his suspicions were, had meant to make sure of Dick, knowing that Yvette alone could not escape him. A few minutes later they heard her knock, and soon all three were in the house.

"Safe enough now," said Fedor laconically as he led the way through piles of stored goods to an upper room at the top of the building.

The room was faintly illuminated by a gleam of moonlight which came through a skylight in the roof, and when a small lamp was turned on Dick looked around him with keen interest. Filthily dirty, and apparently unused for years, the room was crammed with a heterogeneous mass of canvas packages and wooden boxes. The only window was covered with shutters through which circular holes had been bored to admit light, but these were covered over with flaps of felt. The dust of years lay thick everywhere.

Dick's attention was instantly centred on a large, square table in the middle of the room.

Upon the table stood what appeared to be a big camera, its lens pointing to the window, with a screen of ground glass at the back of the camera exposed. A few feet behind, on a tripod, stood a small cinema apparatus with the lens aperture directed at the ground glass plate of the camera. To each ran electric wires from a bracket on the wall of the room. The whole of the electrical apparatus was weird and complicated.

There were also on the table two head telephones connected by wires to the horn of what looked like a large phonograph.

"Now, Mr Manton," said Fedor in a low, intense voice, "I will show you my new apparatus. Mademoiselle Pasquet knows about it."

Dick was breathless with excitement. Yvette's story of Fedor's wonderful invention had filled him with keenest curiosity.

"If you will look through one of the holes in this shutter," Fedor went on, "you will see, directly opposite, the window of Mestich's dining-room. The curtains are drawn, but you will see the room is lighted inside. He and his friends have been there for some time; apparently they have been awaiting Horst." Dick looked through the hole and saw the lighted window. "Now, come and look at the screen," urged the Count.

As he spoke he touched an electric switch. Immediately a soft purring noise came from the camera and on the screen there showed a vivid well-focused picture of a room with about a dozen men seated round a long table. The interior of the closed room was revealed by the new invention. At the head of the table, facing the camera, sat a big, soldierly man whom Dick at once recognised, from his published photographs, as General Mestich.

Fedor rapidly named the others--Bausch, Horst, Colonel Federvany, leader of the Parliamentary Opposition, several officials of the Galdavian Government and War Office, and two or three Jew financiers, one of whom named Mendelssohn Dick knew to be of international reputation.

The marvellous picture was framed in a solid black outline. It gave a curious effect, just as though one were looking from the darkness into a fiercely lighted cave.

Dick was almost stupefied with astonishment.

"Do you mean to say that that is the room in the house on the opposite side of the road?" he asked.

"Certainly I do," said Fedor with a grim smile.

"But how is it done?" demanded Dick, aghast. "The shutters are closed here and the curtains drawn on the other side."

"It's a new electric ray I stumbled upon quite by accident," Fedor explained. "I was experimenting, and found it. It passes quite readily through wood, fibre and fabric, in fact through almost anything except stone, mica, and metal. That is why you see only part of the room; the walls cut off everything except the space directly behind the window. If the table were in the corner of the room they would be safe enough-- if they only knew!"

"Marvellous!" Dick ejaculated.

"This new ray is projected from these two rods of silenium," the Count went on, "and for some reason which I cannot explain it follows the direction of the longitudinal axis of the metal. Thus any object at which the rods are pointed is rendered luminous by the ray on the screen, which is coated with the barium sulphate used in X-ray work. It can be photographed by the cinema and we shall have evidence enough to hang the lot."

Then he paused for a few seconds.

"Now we must begin," he said suddenly. "They are just about to start. Hold the telephone receivers to your ear. Mademoiselle will look after the cinema."

Picking up the receiver, Dick heard a voice speaking clearly and earnestly. It was evidently that of General Mestich, who, as he saw by the screen, was on his feet and speaking. The language, of course, he did not understand, but Fedor, who was also listening, became excited and snapped on a switch which started the phonograph. In the meantime Yvette was turning the handle of the cinema camera.

"Here it comes," Fedor ejaculated a moment later, and Dick saw General Mestich take from his pocket a big blue document which he unfolded and spread on the table before him. Bausch at the same time produced a similar paper.

Then Bausch got to his feet and also spoke briefly. Immediately after the documents were passed round and signed by all present. The treaty was made! But every action of the plotters had been caught by the eye of the camera, and every word they uttered was recorded by the phonograph! The evidence was complete!

"Now, Manton," said Fedor, "we have all we want except Mestich's copy of the treaty which will be signed by the German Secretary of State, as well as Bausch and Horst. To get that and get away is your work. I have to stay in Langengrad and I dare not risk being seen and identified. You understand?"

"Of course," answered Dick. "You have done wonders--absolute wonders! But just tell me how this telephone works."

"That is Mademoiselle Pasquet's invention," replied Fedor. "It is really a secret change-over switch which projects an electric ray which sets the General's transmitter working even when the receiver is on the hook and the instrument would in the ordinary way be `dead.' It can be put in in three minutes; as a matter of fact I slipped it in one day when I called to see the General and was kept waiting. The main wire from the General's 'phone to the Exchange passes over the house and it was easy enough to `tap' it with a fine wire that can be pulled away so as to leave no cause for suspicion. I shall do that now; we shall not want it again."

Soon after, the party opposite began to break up and finally, on the screen, they saw the General standing alone, the treaty in his hand, and a look of triumph and elation on his handsome face. It was the picture of a man who had very nearly reached the summit of his ambitions. A moment later he crossed to the big, high stove, lifted a heavy picture, and slid aside a small door in the panelling of the wall. This disclosed a recess in which the treaty was deposited, the slide was closed, and the picture replaced.

"Clever," said Dick, "but easy now we know. I thought he would put it in a safe. But how are we going to get it?"

Yvette, who had been silent, interposed.

"I think the General's house might unexpectedly catch fire," she said quietly. "That will give Dick a chance to make a dash for the treaty in the confusion."

"I don't see any better plan," Fedor agreed. "It can easily be managed. I have plenty of petrol here, and there is a small leaded window on the ground floor that can be pushed in without making too much noise."

"Excellent!" exclaimed Dick. "I'll manage that. I'll see there's plenty of confusion."

"Very well, that is settled," answered Fedor. "Now I will take Mademoiselle to your car and have everything ready for you to start. It will be touch and go. Here is the phonograph record, with the cinema film rolled up inside it. Take care of them; they are priceless. The film must be developed in Paris."

Then Fedor produced a can of petrol and thoroughly soaked the room.

"This place is going up to-night," he explained. "That police agent will know all about it and it will be searched at once. I can't get my camera away and I don't want it found."

As he spoke Fedor was laying a long strip of fuse from the room to the ground floor. Striking a match he lit the end.

"In half an hour the place will be a furnace," he said coolly.

What to do with the police agent was a problem.

"I can't kill the fellow in cold blood," remarked Fedor, "and I can't leave him here to be burnt alive."

Finally they dragged the man outside and left him lying in the darkest corner of the alley they could find.

"Some one will find him when the fire starts," was Fedor's conclusion.

But some one found him much earlier, and their clemency nearly cost them their lives!

Yvette and Fedor started for the Mohawk and Dick walked swiftly over to the General's house. It was very late and not a soul was stirring in the now deserted streets. Without difficulty Dick found the leaded window and scarcely troubling about the slight noise he made, forced it partly in, poured in a liberal supply of petrol and flung after it a lighted match. Instantly there was a most satisfactory sheet of flame.

A moment later Dick was hammering at the front door, shouting at the top of his voice. He aimed at making all the confusion he could.

Instantly the street was in an uproar. People poured half-dressed from the houses, and from General Mestich's residence came a stream of frightened domestics, screaming in terror and half-choked with smoke.

Slipping unnoticed into the house, Dick made straight for the _salon_. As he entered, General Mestich was in the very act of withdrawing the treaty from the secret receptacle. He turned towards Dick and their eyes met.

Traitor though he was, the Galdavian General was a cool and brave man. His hand dropped to his pocket and a revolver flashed out. But he was just a fraction of a second too late. Dick's hand was ready on his automatic, and as the General's revolver came out Dick fired from his pocket and the leader of the Galdavian revolution fell dead with a bullet through his heart.

A moment later Dick, the precious treaty in his pocket, had joined the shouting throng in the crowded street. As he did so, a burst of flame from the old storehouse announced the success of Fedor's plan and added to the general confusion.

Dick worked himself clear of the crowd and dashed off at top speed for the Mohawk. Yvette was already seated at the wheel, with the engine started ready for instant departure. As Dick sprang into his seat Fedor laid beside him a loaded rifle.

"Ten shots, explosive bullets," he said coolly. "It may be useful if you are followed."

Then hastily they shook hands and the Mohawk leaped forward for the hill road and safety.

The moon was unfortunately very bright, and it was not until they had gone five or six miles that Dick ventured to draw a breath of relief.

"We ought to be safe now," he said. "We must find a place to fly from."

The words were hardly out of his mouth when the roar of a big car behind them caught his ears. They had forgotten the bound and blindfolded police agent.

That very astute individual had been found and released by a passer-by a few minutes after they had left the warehouse! Frantic with rage and determined to catch Dick at all costs, he had acted with wonderful promptness. His first step was to send out cars loaded with armed policemen to block all three roads leading from Langengrad so that Dick's motor should not get away. Had he been found a few moments earlier Dick and Yvette must have been hopelessly trapped. But the delay of a few minutes had given them a priceless advantage.

Looking back as the big car came swiftly on, Dick caught the gleam of rifle barrels in the moonlight. His plan was swiftly made.

At the top of a steep slope, where the road made a sharp curve and dipped into a small depression, Dick bade Yvette halt. Blessing Fedor's foresight, he took the rifle from the car and in the shadow flung himself down on the grass bordering the road. For five hundred yards below him the road stretched in a smooth unbroken descent.

As the pursuing car came into sight Dick took careful aim and fired, aiming not at the men, but at the engine of the car. His first shot was low, and he saw a burst of flame as the explosive bullet struck the road a few yards short of the car.

His second shot got home. The big car lurched, slewed round, and dashing into the side of the road, toppled over. Evidently the explosive bullet had wrecked the steering gear.

He leapt into the car again, but the danger was not over. Checked by the steep rise the big car was only going slowly, and the men inside had evidently escaped unhurt. And they were clearly well led, for a dozen of them dashed into the road and a volley of shots rattled round Dick as he dashed for the Mohawk.

For the moment, racing down the hill, they were safe. But Dick saw, with inward trepidation, that a little farther on the road rose again and they would be a clear mark for their pursuers in the bright moonlight.

His fears were justified. Again a volley of shots rang out and bullets pattered round them. One smashed the wind screen, a second went through Yvette's hat. But they were untouched, and raced on. A moment more and they would be safe. Then another volley rang out and Dick felt a stinging pain in his left shoulder. He had been hit by one of the last shots fired!

They were now out of range and Yvette sent the Mohawk along as fast as she dared until, a few miles farther, she left the high road and drove across the smooth upland turf to the shelter of a small wood where they could convert the car into the aeroplane.

Despite the danger of delay Yvette insisted on binding up Dick's shoulder. Luckily no bone had been touched, but he had lost a lot of blood. By a tremendous effort of will he managed to help Yvette until the aeroplane was ready, and then climbing into his seat collapsed in a dead faint.

When he came to his senses again it was daylight and the Mohawk was flying steadily high above a carpet of white mist which hid the ground. Yvette, crouched over the duplicate control lever, nodded and smiled.

"Better now?" she called.

"A bit rocky," laughed Dick. "Where are we?"

"We ought to be about over Scutari according to speed and compass bearings," was Yvette's reply, "but the mist has been baffling me. Still, I don't think we are far out."

"How long have we been flying?" asked Dick.

"About two hours," Yvette responded, "and we have been doing about seventy. That should bring us very near the coast."

After a stiff dose of brandy and a mouthful of food Dick felt better. A few moments later he pointed downwards.

"Lake Scutari!" he remarked, as he recognised the long narrow sheet of water at the head of which the ramshackle half-Turkish town stands.

The mist was already breaking as, at ten thousand feet elevation, they swept out over the Adriatic and headed for the Italian coast. Then Yvette began a rapid call on the wireless set with which the Mohawk was fitted and placed the head-telephones over her ears.

"Got him! He's there all right!" she exclaimed triumphantly a few minutes later. "He answers `O.K.'"

It was Jules, who for three days had been cruising off Cape Gallo in a motor-launch, ready to dash to their rescue if anything went wrong as they crossed the Adriatic, and who was now heading in their direction as fast as his engines would drive him.

Suddenly Yvette uttered an exclamation of alarm.

"Dick," she said, "our petrol is giving out. There is none left in the number four tank and five and six will only carry us about seventy miles."

Evidently the bullets of their pursuers had pierced the tank which was now empty and the precious spirit had drained away unnoticed.

The situation was now serious indeed. Could they get to Jules in time? A wireless message bade him hasten.

"Ten miles more, Dick," said Yvette at last, "and then I can make three miles and the glide as we come down. It's lucky we are so high; we ought to do it."

Then seven or eight miles away a column of vapour rose from the water ahead. Jules had fired a smoke bomb to guide them! Their petrol was almost gone. But as the engine flickered out and stopped Yvette, with a cry of joy, pointed to a tiny dot on the sea which they knew was Jules rushing to their help. A rocket shot up from the launch.

"He sees us!" said Dick, as Yvette set the Mohawk on a flat downward slant. Two minutes later they struck the water with a mighty splash just as the motor-launch tore up, flinging a cloud of spray into the air as she rushed to their rescue. They were safe and they had saved a throne! But the gallant Mohawk sank to the bottom of the Adriatic.

------------------------------------------------------------------------

There was no revolution in Galdavia. With the damning evidence of the film and the phonograph record the Allies acted promptly, and with the traitor Mestich dead the plot went to pieces. King Milenko rules to-day over a contented, happy and prosperous people, and his early follies laid aside has become a capable and popular ruler. Fedor they never saw again; he was killed in a motor smash a week after they left, and the secret of his wonderful invention died with him.

CHAPTER THREE.

THE SEVEN DOTS.

In a cosy little house at Veneux Nadon, near Moret-sur-Loing, in the great Forest of Fontainebleau, Dick, Yvette, and Jules were seated in earnest conversation. They made a remarkable trio. Dick was unmistakably English, Yvette and her brother as unmistakably French--the girl dark-haired and dark-eyed, and with all the grace and vivacity which distinguish Frenchwomen of the better class. Her brother, quiet and dreamy, lacked his sister's vivacity, but there was a suggestion of strength and iron resolution in the firm mouth and steely eyes.

"It will be terribly dangerous, Dick," said Yvette, with an altogether new note of anxiety in her voice.

"I suppose it will," replied Dick, "but,"--and his voice hardened as he spoke--"I don't see what else we can do. We cannot run the risk of seeing a perfected helicopter in German hands. It would be too fearful a weapon. We must get hold of the plans and destroy the machine, whatever the risk may be."

Strange stories had come through the French Secret Service of a new and wonderful type of aircraft which was being tested with the utmost secrecy somewhere in the neighbourhood of Spandau, the great military town near Berlin. Of its precise character little was known or could be ascertained, and even Regnier, the astute and energetic head of the French Secret Service, had at length to confess himself utterly beaten. His cleverest agents had been baffled; more than one was in a German prison, with little hope of an early release. In the meantime the mysterious machine flitted about the neighbourhood of the great garrison, always at night, appearing and disappearing under circumstances which proved conclusively that it must be of a type which differed widely from any yet known to the public.

"We must go, Dick," said Yvette, "and Regnier is extremely anxious that you should help us. His trouble is that while he has dozens of capable men at his command none of them has a really expert knowledge of aviation. He thinks that if you once got a good look at the machine you could form a complete idea of what it really is."

"Very well," said Dick, "we will look upon it as settled. We must work out a plan."

For many months Dick Manton had been working steadily and secretly at Veneux Nadon under the auspices, though not actually in the employ, of the French Secret Service. He had offered the plans of the Mohawk to the British War Office, only to be met with a reception so chilly as effectually to discourage him from proceeding further in the matter. Regnier, however, was a man of a different stamp from the British bureaucrat--keen as mustard and with the saving touch of imagination which is characteristic of the best type of Frenchman. He had unbounded faith in Yvette, who had for some time been one of his most trusted lieutenants, and when, angry at the attitude of the British War Office, she had given him a hint of what the Mohawk could really do, he had offered Dick the fullest facilities for continuing his work. Under the circumstances Dick had felt that to refuse would have been absurd.

Veneux Nadon was a lonely little spot. Here Dick, though only thirty miles from Paris, found himself in complete seclusion, with a well-equipped workshop in large grounds completely buried in the lovely forest, and thoroughly screened from prying eyes. Regnier had put the matter to him quite plainly.

"You are an Englishman, Monsieur Manton," he had said, "and I will not ask you to sell your secret to France. But we are willing to bear the expense of perfecting your invention on the distinct understanding that when the time comes England shall have the option of sharing in it to the exclusion of all other countries except France. When you are ready we will officially invite the British Government to send a representative and will give them the opinion of coming in on equal terms. I do not think we can do more or less."

So it was settled, and for many months Dick and Jules had toiled on the building of a new Mohawk whose performances far surpassed those of the machine lost in the Adriatic. It was now completed and its preliminary tests had satisfied them that they had forged a weapon of tremendous potency.

The machine was of the helicopter type. The idea, of course, was not new, but Dick had solved a problem which for many years had baffled inventors whose dream it was to construct a machine which should have the power of rising vertically from the ground and remaining stationary in the air.

Driven upward by powerful propellers placed horizontally underneath the body, the Mohawk was capable of rising from the ground at a tremendous speed. Once in the air the lifting propellers were shut off and the machine moved forward under the impulse of the driving screws placed in the front and rear. These screws were the secret of Dick Manton's triumph. They were of a new design, giving a tremendous ratio of efficiency. In size they wore relatively tiny, but possessed far greater power than any propeller known. The machine itself was nearly square. The body was completely covered by the big, single plane, measuring about twenty feet each way. This was the outside size of the machine and so perfectly was the helicopter controlled that Dick had repeatedly brought it to earth in a marked space not more than thirty-two feet square.

Fitted with the new silencer which Dick had discovered and applied to the old Mohawk with such signal success, the engine was practically noiseless. At high speed the tiny propellers emitted only a thin, wailing note, barely audible a few yards away. Time and again Dick had sailed on dark nights only a few feet above the house roofs of Paris and had found that the noise of the ordinary traffic was amply sufficient to prevent his presence being discovered.

To ensure absolute secrecy the various parts of the machine had been made in widely separated districts of France, and had been brought from Paris to Veneux Nadon, where Dick and Jules had carried out the erection of the machine alone. The very existence of the new aeroplane was utterly unsuspected by the few villagers who lived in the neighbourhood.

Keenly interested in his work Dick had thoroughly enjoyed the peaceful life in the depths of the beautiful forest. He and Jules had become the closest of friends, and with Yvette, whose winning personality seemed to bind him to her more closely day by day, they made up a happy house party. They were looked after by a capable old peasant woman who was the devoted slave of all three, but whose admiration for Yvette seemed to rise almost to the point of veneration.

On the day following the conversation recorded above, they were surprised to receive a visit from Regnier himself--an alert, dark-eyed man who seemed seriously perturbed.

"There is no time to be lost," he declared. "I hear to-day from Gaston that he has managed to get a near view of the new German machine. He says it rose apparently from the flat roof of a house standing in its own grounds outside Spandau. He happened to be near and caught sight of it just in time. Of course it was dark and he could see no details. But he is positive that the machine rose nearly straight up from the flat roof at an angle far too steep for any of our machines. That alone is sufficient to show that the Germans have got hold of something new and valuable. He waited for a long time, and finally saw the machine return. He declares it landed again on the roof. Evidently, Monsieur Manton, they have found out something along the lines of your invention, even if they have not actually got your secret."

"How far away was Gaston when he saw it?" asked Dick.

"It must have been at least a quarter of a mile," replied Regnier, "as the grounds are very extensive. Gaston dared not venture an attempt to get inside; the high fence is utterly unscalable, and the two lodge gates are always kept locked and there is a keeper at each."

"And he heard the engine?"

"Yes, he says so specifically," replied the Chief.

"Well," said Dick, "at any rate we are ahead of them to that extent. If it had been my machine he would not have heard the engine at all at that distance."

"However," he went on, "it is evidently time we acted. Now, Monsieur Regnier, Mademoiselle Pasquet has told me what you want. I am willing to go. But I shall have to take the Mohawk. How are we to hide it? I can get over and back at night safely enough, but to hide the machine in the day-time will be another matter."

"Gaston can arrange that," the Chief declared. "You know he has a farm a short distance outside, Spandau. There is a big barn there with no sides, and your machine can be easily dragged into it and concealed during the day. You know Gaston is passing as a German farmer. He has acted for years for us in this way and has never even been suspected. But you could not stay long."

"Very good," said Dick. "I think the best plan will be for Jules to go by motor and for Mademoiselle to go separately by train. They must find out somehow exactly where the German plane is lodged and, if possible, where the plans are likely to be kept, and I must act accordingly. In any case, there will be no difficulty in smashing up the machine, but unless we destroy the plans as well they will be building another too soon to suit us. I will go to Verdun and wait there with the Mohawk until the time comes for me to fly over."

Jules and Yvette left the next day. Jules' car was quite an ordinary one, but it had one important detail added. In the hollow flooring was cunningly concealed a small but powerful wireless telegraph set, the power for which was supplied by the engine. It was highly efficient, but had one serious drawback; it could only be used while the car was at rest owing to the necessity for running an aerial wire up some tall structure, such as a building or a tree. This, in a country where every one was specially suspicious of spies, was a serious peril.

Three days later seven mysterious dots began to excite the ungovernable curiosity of the wireless world!

Jules and Yvette, on arrival in Berlin, had taken rooms adjoining one another at the "Adlon," the big cosmopolitan hotel which is always crowded with visitors from every country under the sun. Yvette posed as a school teacher on an educational tour, but her position was one of great danger. It was impossible to disguise her face, and although she had done what she could to destroy her French individuality by wearing peculiarly hideous German clothes, there was the ever-present danger that she would be seen and recognised by some of the many German agents who during the war had learnt to know her features, and who had good reason to remember her daring exploits in Alsace.

At the same time, in order to have a possible retreat in a humbler neighbourhood, Yvette had hired a room in one of the mean quarters of the town, putting in a few miserable sticks of furniture and giving out that she was a sempstress employed at one of the big shops.

She and Jules had decided never to speak in public. It was essential, however, that they should be able to communicate freely, and through the wall between their rooms Jules had bored with a tiny drill a hole through which he had passed a wire of a small pocket telephone. They could thus talk with ease and with the doors of their rooms locked they were absolutely safe from detection so long as they spoke in a whisper.

It was on a dark night, the sky obscured by heavy masses of clouds, that Dick rose in the Mohawk from the Forest of Fontainebleau and headed for Verdun. A couple of hours' flying brought him over the fortress and he descended in a clearing in a dense wood where he was welcomed by Captain Le Couteur, the chief engineer of the military wireless station. Covered with big tarpaulins, the Mohawk was left under the guard of a dozen Zouaves, and Dick and Captain Le Couteur motored to the citadel.

Here the Captain took Dick directly into the steel-walled chamber deep under the fortifications which was the brain of the defences of Verdun. It was the nucleus of the entire system of telegraph and telephone wires which, in time of war, would keep the commander of the troops in the district fully informed of everything that was happening in every sector of the defences. The innermost room of all, where none but the Captain himself had access, contained the secret codes which dozens of foreign agents would have willingly risked their lives to possess. Their efforts--and they knew it--would have been in vain, for the chamber was guarded day and night by a band of picked men whose fidelity to France was utterly beyond the possibility of suspicion.

"Your messages have already started--the seven dots at intervals of seven seconds," said Captain Le Couteur when they were comfortably seated in the innermost room. "I got half a dozen test calls last night and everything seems to be working well. I expect they are arousing some interest, for operators all over Europe will be mystified. There will be another call about nine o'clock and in the meantime you had better get some sleep. I will call you if anything happens."

Dick stretched himself on a couch and slept peacefully. Nine o'clock found him with Captain Le Couteur seated in the innermost room at a table covered with delicate wireless apparatus. Turning a switch, the Captain lit up the row of little valves, put the receiving set in operation, and assuming one headpiece himself, handed another to Dick.

He placed his hand upon one of the ebonite knobs of the complicated apparatus and slowly turned it. Then he turned a second condenser very carefully.

"We are on the ordinary six-hundred-metre wave-length now," the Captain explained, "and shall remain so until we get our seven dots. I am bound to keep the machine so or I should miss other messages I ought to hear. But we will change as soon as we get your signal."

Presently they came, sharp and clear, dot-dot-dot-dot-dot-dot-dot. Immediately Captain Le Couteur made some swift adjustments.

"Now listen," he said, "we are on a three-hundred-and-fifty-metre wave-length."

A moment later came three M's--three pairs of dashes.

"That's Code Five," said Captain Le Couteur. "Now we shall get the real message."

It came in what to Dick was a gibberish of letters and figures, but Captain le Couteur wrote it down and then, decoding it, read it off with the skill of the expert. It ran:

"M M M begins Have located the machine stop Apparently entirely new type stop Tell Manton to be ready stop M M M ends."

"That's our newest code," the Captain explained, "and this is the first time it has been used. Jules learnt it only just before he left. It is very unlikely that the message has been picked up by anyone else, as the wave-length is quite low, but even if it was, no one could decipher the code from such a short message. They would want one very much longer, and even then it would probably take at least a week or ten days of very hard work by a lot of experts."

And he paused.

"I think it would be well now for one of us to be constantly here," he went on. "Perhaps, too, you would like to overhaul your machine so as to have it absolutely ready to get away at a moment's notice. My fellows will give you any help you want and they are all absolutely to be depended upon not to talk."

Dick soon had the Mohawk ready; indeed there was not much to do after such a short trip as the flight to Verdun. The rest of the day he spent chatting with Captain Le Couteur, finding him a delightful companion and full of enthusiasm on the subject of wireless, of which his knowledge seemed boundless. Dick felt he could never tire of admiring the wonderfully ingenious devices which the other had invented and put into operation in his underground fortress.

Several more messages, chiefly brief reports, were received from Jules, always heralded by the seven dots and begun with the three M's which signified the secret code number Five. For a few hours everything seemed to be going well. Then, towards evening came graver news, which on being deciphered, read:

"M M M begins Much fear Yvette suspected stop Tell Manton to be ready instant action stop M M M ends."

It could only mean, they realised, that Yvette had been recognised by a German agent and was being closely watched. The position was dangerous.

Dick spent the next few hours in an agony of suspense. But he could do nothing. His first instinct was to fly to Berlin. But Le Couteur's iron common-sense showed him clearly enough that to do so would be futile. To keep the Mohawk in Germany, even for a single day, would be risky; to try to hide her there for perhaps a week till they got a chance to rescue Yvette would be suicidal.

A sudden swoop, swift and relentless action, and a quick escape were the essentials of success.

Captain Le Couteur was scarcely less anxious than Dick himself. He had known Yvette since she was a child; they came from the same town in Alsace. But he possessed a brain of ice and restrained Dick's impetuosity, though guessing shrewdly at its cause.

"The time is not come yet," he declared. "This is a bit of business which must go to the last tick of the dock. Mademoiselle herself would never forgive us if we spoilt everything by undue precipitation, and, after all, Monsieur Manton, France is of even more importance than Mademoiselle Pasquet, much as I admire her."

"I know," Dick admitted. "But when I think of her, with her war record, which they know all about, falling into the hands of those brutes, I can hardly sit still."

"They have not got her yet and she is very clever," replied Le Couteur. "Let us hope that she will give them the slip."

But about ten o'clock the following morning the dreaded blow fell.

They were seated in the underground chamber, Dick ill at ease and full of gloomy forebodings. The apparatus set to receive messages on three-hundred-and-fifty-metres. Suddenly a buzzing noise was emitted from the loud-speaking telephone on the bench.

Seven dots, seven times repeated, clicked out strong and dear!

Surely seconds had never passed so slowly! It seemed an age before Captain Le Couteur, his face white as chalk, took down the message which followed, and then referring to the code, read:

"Yvette arrested this morning by Kranzler."

Dick turned dizzy and the room spun round him as the dreadful significance of the words struck him. Kranzler, of all men! The murderer of Yvette's father and mother, the man whom she had beaten over and over again at his own game of espionage during the war, the man whose sensational attempt to dispose of Rasputin's stolen jewels had been foiled by Yvette's skill and daring! He was, as they knew, a desperate brute who would stick at nothing to feed his revenge.

Dick was rushing from the room, determined at all hazards to leave for Berlin at once, when Le Couteur seized his arm in a grip of iron.

"Steady, Manton," he said sharply. "Don't be a fool. You'll spoil everything. Sit down and wait for more news."

The words brought Dick to his senses.

"I'm sorry, Le Couteur," he said, "but I think I went a bit mad. You are quite right. But Kranzler--of all men! You know the story, of course?"

Le Couteur nodded.

"It could hardly be worse," he admitted, "and there's no use disguising the fact. But we must wait for more from Jules. In the meantime I am going to talk to Regnier. He must have more men on the spot. At all costs Mademoiselle must be rescued."

They were soon in touch with the Chief in Paris, who was horrified at the news.

"I will get some more men over at once," he said. "But we can do nothing until we find out where they have taken her. Jules will realise that. You are certain to get another message from him before long."

It was not until later that day that they learned how the arrest had been effected. Yvette, as soon as the position of the German plane had been located, had managed in the guise of a girl seeking work, to scrape acquaintance with one of the maids employed at the big house where the aeroplane was lodged. The girl had actually taken her up to the house and Yvette had coolly applied to the housekeeper for employment. There was, as it happened, no vacancy, but Yvette had used her eyes to good purpose. In the walk from the lodge to the house and back she had caught sight of the shed in which, obviously, the aeroplane was housed, and had noted its exact position in the extensive grounds. Hurrying back to the hotel she had communicated this information to Jules and both were filled with excitement at the important step forward they had made.

Sitting in the lounge of the "Adlon" next morning Jules had seen Kranzler enter. He had started at once to warn Yvette to "lie low," but was just too late. Yvette at that moment came down the staircase and before Jules could interpose had met Kranzler face to face. She was instantly recognised.

With a grin of delight on his evil face the big German bowed profoundly.

"This is indeed a pleasure, Mademoiselle Pasquet!" he said ironically.

Yvette very coolly tried to carry it off.

"Monsieur has, I think, made a mistake," she said in German.

"It's no use, Mademoiselle," was the harsh reply, "I know you perfectly. You must come with me--or shall I call the police?"

There was obviously nothing for it but to obey, and Yvette was forced to leave the hotel in the clutches of the one man in all Germany she had the greatest reason to fear.

Jules acted promptly. Slipping out of the hotel he hurriedly wheeled to the front a motor-bicycle he had hired to enable him to travel speedily between Berlin and Spandau. He got round just in time to see Kranzler put Yvette into a taxi, and followed them until they alighted at the door of the house in the Koeniggratzer-strasse which was the head-quarters of the German Secret Service. Yvette was taken inside.

To get the news to Dick was now Jules' first consideration. Knowing something of the methods of the German Secret Service he was reasonably sure that Yvette would be put through a long examination before she was taken to prison, and he decided to run the risk of being absent for a short time to get his message away. He drove hastily in his car out into the country until he found a tree to which his aerial wire could be attached and got off the brief message which conveyed the news to Verdun. Then he returned to watch, and ascertain where Yvette was to be imprisoned.

The taxi was still outside the door when he got back to the Koeniggratzer-strasse. As an excuse for waiting he feigned engine trouble and tinkered with his machine, keeping all the time a close watch on the door opposite.

He had not long to wait. In about half an hour Yvette was brought out, still in the custody of Kranzler, and driven away. Jules followed, and, at length, had the satisfaction of knowing that Yvette was in the big prison outside Spandau. It was a melancholy satisfaction, it is true, but to know where she was was of supreme importance.

Driving to Gaston's farm he soon informed Verdun where Yvette was located and then turned to discuss the position with Gaston.

To his intense surprise and delight, Gaston was able to give him some comfort.

"Of course, it is a great misfortune," he said, "but it might be worse. They have taken her to the one prison in Germany where we have been able to keep a thoroughly trustworthy agent. He is a warder who passes as Herman Fuchs; his real name is Pierre Latour. We shall soon know all about Mademoiselle."

The front of the prison was in dear view from Gaston's farm. Going outside, he called on Jules to help him to move one of three large barrels, each containing a big flowering shrub, which stood side by side in front of the house facing the prison. One of these was taken away, leaving only two.

"We shall have Pierre over here this evening," Gaston chuckled. "That's the signal that I want him."

Sure enough, soon after dark, Pierre appeared. A few words explained the situation. He was off duty now for the night and free to do as he pleased.

"Leave it to me," he said. "I will be back in an hour."

He returned with a rough plan of the section of the prison in which Yvette was confined. Her cell occupied a corner on the first floor at the head of a flight of steps leading down to the big courtyard. If Yvette could get out of her cell it would be an easy matter to reach the door leading to the yard. But to get over the high wall, quite unclimbable, was a difficult problem. The entrance from the roadway was always guarded by two warders who occupied little separate lodges placed one each side the gateway.

"I can get her out of her cell," said Pierre, "but how to get her out of the yard I don't know. I can get a false key to her during the day, but if I were found in that quarter of the prison at night it would mean instant dismissal. On that point the rules are inflexible and we cannot risk it."

"No," said Gaston, "it is absolutely essential that you shall remain in the prison. But I think I can see a way."

He crossed the room to an old-fashioned bureau and produced from a drawer what looked like a heavy short-barrelled pistol.

"Gas!" he said laconically, "fire that at a man's face within five yards and he will drop like a log. It holds four shots and makes no noise. If Mademoiselle can get this she can knock out the two men at the lodge and easily slip out. You can bring her straight here, and we can hide her until she can get away."

"She cannot hide that in her cell," said Pierre, "but I can hide it in the courtyard. Write her a letter telling her exactly what to do and where the pistol will be. I can slip into her cell a skeleton key which will open the door and also the door at the bottom of the steps. But you must manage the rest; I cannot do any more. She must get out immediately after the last visit of the warders at nine o'clock."

"Thanks very much, Pierre," said Jules. "I can see no other way, and at all costs we must try to get her out. Neither my sister nor myself will ever forget."

Speedily a letter was written which gave Yvette full details of what was proposed, and Pierre was about to leave when Jules asked him if he had heard anything of the secret aeroplane.

Pierre shook his head.

"There are a lot of privately owned aeroplanes about here," he said, "but I don't know anything more than that. I have seen the one you refer to going up at night--the house is in plain view from my room on the first floor of the prison--but I never heard there was any secret about it, and there are so many aeroplanes about that no one takes any notice of them."

Jules told him all they had found out, and of their suspicions, and found Pierre was able to give them valuable information.

The aeroplane shed, he told them, was just where Yvette had located it. Above it--and this was important--were some rooms which were used, apparently, as offices.

"I have often," said Pierre, "seen a man come from the offices with what looked like plans, make examination and measurements of the machine, and then go back. But I never took much notice; I had no reason to."

Pierre left, taking with him the letter to Yvette. For an hour Jules and Gaston discussed the situation.

"We must get her out to-morrow," declared Gaston, "or else they may take her away and we shall not be able to find out where she is. Manton ought to fly over to-morrow night. If we can get Mademoiselle Pasquet out she can hide here quite safely for a few hours, but there will be a very close search when her escape is discovered."

"I'll get the message to Manton at once," said Jules.

And so it happened that Dick and Le Couteur, who had been waiting for hours in a state of tense anxiety, received a few minutes later the call.

"M M M begins To-morrow night stop Come early as possible stop Three lights in triangle safe stop Four keep off M M M ends."

"At last," said Dick grimly, with a look on his face that boded ill for some one. He looked drawn and haggard, and even Le Couteur could hardly repress a shudder at the savage determination that blazed in his eyes.

For Yvette the next day was one of misery. Time after time she was dragged from her cell and taken before the Governor of the prison, and Kranzler, to be pitilessly cross-questioned and even threatened with violence. But even though she knew well that the two brutes were quite capable of carrying out their threats nothing could break the spirit of the French girl. To all their questions and menaces she turned a deaf ear and nothing they could say would induce her to affirm or deny anything. Utterly worn out she was at length roughly bundled back into her cell, where she dropped exhausted on the miserable apology for a bed. At least she was alone.

It was about five o'clock and she had fallen into an uneasy doze, when she was awakened by a slight noise at the door. She saw the observation grille slide back and, pushed through the grating, a tiny parcel fell with a subdued clink on the floor. Then the grating was closed.

Hastily she sprang to her feet and seized the parcel, a new hope surging in her breast. It could only mean help!

Inside the parcel was a letter, unsigned of course, but in Jules' handwriting, and a small key.

Nine o'clock came, and with all the wearisome ceremony dear to the German heart, the guard, accompanied by a wardress, made its final inspection for the night. A few minutes after the big prison was as silent as the grave.

Half an hour later Yvette cautiously fitted the key into the lock. It had been well oiled, and the door swung open without a sound. Creeping down the flight of steps Yvette found that the key also opened the door at the bottom, and in a moment she was in the yard.

Rain was falling heavily. There was not a ray of light in the yard excepting a faint gleam which showed the position of the warders' lodges.

Before leaving her cell Yvette had pulled her stockings over her boots, and moving without a sound she groped her way along the wall. A few feet from the door she found the big stackpipe which brought the rain water from the roof. Stooping she lifted the iron grid of the drain and thrust in her hand. Her fingers closed on the butt end of the gas pistol.

Silently, following along the wall in preference to crossing the courtyard, she stole towards the lodge. Complete surprise was essential.

With the pistol ready in her hand, she softly opened the door of the lodge on the right of the gateway. Luck was with her again. The two men, in defiance of rules, were in the same lodge talking quietly.

The noise of the door opening brought them to their feet with a jump. But they were too late. Only ten feet away from them Yvette pulled the trigger twice in rapid succession. There was no more noise than a slight hiss as the gas escaped and the two men dropped insensible. Snatching up a bunch of keys from the table, Yvette herself half-stifled, quickly got outside and closed the door. A moment later she had opened the wicket-gate and slipped through. She almost fell into the arms of Jules and Gaston, and at top speed the three raced through the rain for Gaston's farm.

Luckily, the pouring rain swiftly obliterated their footprints, but they had hardly got into hiding, wet through but triumphant, when pandemonium broke out in the prison, and the frantic ringing of the big bell announced the escape of a prisoner. The two warders, of course, had speedily recovered, and hastened to tell their story, and a quick search had revealed that Yvette's cell was empty. A few minutes later search parties were hurrying in every direction in pursuit of the fugitive.

Gaston's farm, lying close to the prison, was naturally one of the first places to be visited. Gaston, smoking peacefully by the fireside, soon heard, as he expected, the savage clamour of dogs in the farmyard mingled with agonised cries for help.

He hurried out. Two warders, one of them badly bitten, were backed against the fence, hardly keeping at bay with their sticks a couple of powerful dogs.

Gaston called off the dogs and, full of apparent solicitude, expressed his regret. He listened to the guards' explanation.

"She cannot have been here," he declared, "the dogs would have bitten her to pieces. But, of course, we will look round if you like."

The guards, however, were more than satisfied. Gaston's argument was backed by their own experience, and they were quite ready to be convinced if they could only get away from the ferocious dogs who continually prowled about snarling as though even the presence of their master was hardly sufficient to protect his visitors. They little dreamed that the savage brutes would indeed have torn Yvette to pieces had not Gaston thoughtfully taken the precaution to lock them up before he and Jules started to rescue her!

Away at Verdun Dick stood beside the Mohawk waiting impatiently in the dark. Time and again he had tested every nut and screw in the machine; time and again he had run the powerful engine to make sure that it was in working order.

At last the longed for moment for action came. Anything was better than long drawn-out suspense.

He wrung Le Couteur's hand as he stepped into the machine.

"I'll be back with her by dawn," he said, "or else--" there was no need to finish the sentence.

He had not gone five minutes before Le Couteur received a message from Jules announcing that Yvette had escaped. If only Dick had known!

It was raining hard when the Mohawk rose into the air, but Dick was beyond caring for the weather, and anxious only for Yvette, he sent the helicopter tearing through the darkness eastward to Berlin. He drove almost automatically, his thoughts intent on the girl ahead of him.

As he approached Berlin, the weather cleared and the rain stopped. All around him were the navigation lights of the German mail and passenger planes, hurrying to every quarter of the Empire, and, even in his anxiety, Dick was conscious of an uneasy feeling of irritation at the thought that England was being left so far behind in the race for the mastery of the air.

Then he caught sight of the great beams of light that marked the position of the huge Berlin aerodrome, and a few minutes' flying brought him above Spandau. He circled twice, looking for Gaston's signals, and at last he dropped lower, caught the gleam of the three lanterns which Gaston had placed to guide him, and brought the machine swiftly down beside the big barn. Then he leaped from his seat.

He nearly gave a shout of joy that would have aroused every German within a mile! For there, in the light of the lanterns, stood Yvette herself.

There was no time for explanation.

"Now's your chance," gasped Jules, wild with excitement, "the German plane has just gone up!"

Dick's face hardened instantly.

"Get in, Yvette," he said curtly.

Yvette stared in utter astonishment. This was a new Dick with a vengeance! All his usual graceful courtesy had dropped from him in the instant; the sheer fighting spirit was on top and Dick was, for the moment, the officer giving commands to his subordinates. His face was set like granite, and into the keen eyes there came a look Yvette had never seen there before. The cheerful, laughing "pal" had gone; in its place stood the fighting machine, pitiless and efficient.

For an instant the girl was almost on the edge of rebellion; then she turned, and, without a word, took her place in the machine. As she did so, she caught Dick's eye. For an instant the stern face relaxed; then the iron mask shut down again.

For five minutes, while Yvette put on her leather helmet, Dick studied the plan which Jules showed to him by the light of a shaded lantern. When the Mohawk jumped into the air every detail of it was photographed indelibly on his brain.

For three thousand feet the Mohawk shot upward at a speed which left Yvette dizzy and breathless. Then they hung motionless, as Dick peered anxiously earthward. Were they high enough?

With a smothered exclamation Yvette pointed downward. Far below them a light was circling swiftly, darting hither and thither like a will o' the wisp. No mail plane would behave like that. Dick decided that here was his quarry.

Silently the Mohawk came down till it was not more than five hundred feet above its unsuspecting prey, the loud drone of whose engine came clearly on the air. Dick swung round in a circle, following every movement of the machine below, with a swift precision which Yvette keenly appreciated.

Dick had made up his mind that the offices above the aeroplane shed probably held the key to the problem they had to solve. He knew he could destroy the machine itself. But that would not be enough if the plans remained intact; a new machine could quickly be built. If he could destroy the plans, on the other hand, there would be at least a lot of delay, which would enable the French agents to perfect their plans for discovering the secret. In all probability, he reasoned, the office would serve as the draughtsmen's workroom, and if this were so, a well-placed bomb might destroy the labour of months.

So he watched and waited, until at length they saw the German aeroplane going home. It came down in a wonderfully steep descent which was enough to tell Dick that the Germans had indeed made a discovery of great importance, and landed so slowly that Dick could hardly believe his eyes. But, at least, he saw enough to be sure that the descent was not the vertical drop of his own helicopter. His secret remained his own!

Close beside the shed a couple of hooded airmen alighted. Lights were switched on and they began a careful examination of the machine. Five hundred feet above Dick watched the figures with interest.

Suddenly the men below stiffened and looked skyward, listening intently. Evidently they had caught the faint sound of Dick's propellers.

A glance through his bomb sights showed Dick that he was in the position he desired. There was now no possible escape for the craft below.

Then one of the men pointed upward. Even in the darkness he had caught a glimpse of the Mohawk.

Dick's hand shot to the bomb controls and he pulled a trigger. A petrol bomb fell squarely on the German plane and burst with a soft explosion, barely audible.

A sheet of fire followed, and in an instant the German plane was a mass of flames, fed by the petrol which streamed from its tanks. One of the Germans was caught in the outburst and apparently died almost instantly.

The second man, however, dashed into the office. The Mohawk moved forward a few feet and three more bombs fell in quick succession, right on the roof of the shed. Then, her work done, she rose high into the air and Dick and Yvette watched the results.

The shed below them was already a furnace. Apparently there must have been some petrol tanks there, for no ordinary building could have burned so furiously. In a few minutes nothing remained but a heap of glowing embers.

Dick watched keenly for the man who had run into the office, but he never reappeared, and it was evident that, trapped by the flames, he had been unable to get out in time, and had perished. Dick little suspected at the time how important the fate of that man was to prove.

Then Dick set the Mohawk at top speed for home. Just as dawn was breaking Verdun loomed ahead. Yvette was saved.

Two days later the _Berliner Tageblatt_ told how the famous scientist, Professor Zingler, had perished in a fire which had destroyed his laboratory at Spandau. The fire was attributed to an explosion of petrol on the professor's aeroplane which had set light to the office. Unfortunately, the paper added, all the professor's valuable papers and books had been lost.

The secret of the Zingler aeroplane had perished, and the seven dots were never heard again.

CHAPTER FOUR.

THE SORCERER OF SOHO.

"Unless we can solve this terrible mystery in the course of a few weeks, it is hardly too much to say that England is doomed."

The speaker was the white-haired Professor Durward, the distinguished head of the Royal Society. He sat facing the Prime Minister in the latter's room at 10, Downing Street. Round the long table were grouped the members of the Cabinet. They were men who had lived through stormy and troublous times and had met stories of disaster without flinching. But, as they admitted afterwards, none of the terrible tidings of past years, when the fortunes of the Empire seemed to be tottering, had affected them to the same extent as the few brief words with which the distinguished savant summed up the long deliberations on which they had been engaged. They seemed pregnant with the very message of Fate. Almost they could see the writing on the wall.

"But, Professor," asked the Premier, "do you really mean that nothing whatever can be done to check or prevent this terrible malady?"

"Nothing, so far as I am aware," was the reply. "As you know the most distinguished men of science in England have been at work on the problem. We had a very full meeting last night, and the unanimous verdict was that the disease was not only absolutely incurable, but that nothing we have tried seems capable of affording even the slightest alleviation. The deaths reported already amount to nearly half a million; though the truth is being carefully concealed from the public in order to allay panic, yet practically every community in which the disease has appeared has been virtually wiped out. Curiously enough it does not seem to be spread by contagion. In spite of the rush of terrified people from districts in which it has appeared, no cases have shown themselves except in towns or villages where the mysterious violet cloud has been observed. That phenomenon has been the precursor of every outbreak."

A month before, in the tiny village of Moorcrest, buried in the recesses of the Chilterns, an unoccupied house had suddenly collapsed with a slight explosion. No one was in the house at the time, and no one was injured. As to the cause of the explosion no one could form an idea. Nothing in the nature of the remains of a bomb could be discovered, and there was no gas laid on in the village.

But the few villagers who were about at the time spoke of seeing a dense cloud of pale violet vapour pouring from the ruins. On this point all observers were agreed, and they all agreed, too, that the cloud was accompanied by a powerful smell which strongly resembled a combination of petrol and musk. That was all the evidence that could be collected. No harm seemed to follow and the matter was speedily forgotten.

Very soon, however, the incident took on a new and sinister significance.

A week later a similar explosion took place in Ancoats, a poor and densely crowded suburb of Manchester. In every respect this incident duplicated the happening at Moorcrest. Naturally, it created something of a sensation, and the papers, recalling the Moorcrest mystery, made the most of it.

During the next fortnight similar explosions, all bearing the same distinguishing features, occurred in various parts of England. Sometimes there would be three or four in a single day in the same, or closely adjoining, areas. The public became excited. Not a single person was injured, the damage done was apparently trifling, since all the houses destroyed were of the poorest class. It looked like the work of a maniac--purposeless and without the slightest trace of a motive. People spoke of Bolshevists and Communists. But what Bolshevik or Communist, others asked, would waste time and effort to inflict such absurd pinpricks on Society?

They were soon to be undeceived. An enemy of Society was indeed at work armed with a weapon of a potency which far outstripped the paltry efforts of the Terrorists of old, to whom the bomb and the revolver were the means of world regeneration.

The explosion at Moorcrest took place on May 2nd.

Twelve days later, on May 14th, Doctor Clare-Royden, who was in practice at Little Molton, a village about four miles from Moorcrest, received an urgent message from an old patient summoning him to Moorcrest.

Doctor Royden, jumping on his motor-bicycle, answered the summons at once. A terrible surprise awaited him.

Practically every inhabitant of the village, about a hundred people in all, were in the grip of a fearful and, so far as Doctor Royden's knowledge went, wholly unknown malady.

Its principal symptoms were complete paralysis of the arms which were strained and twisted in a terrible manner, fever which mounted at a furious speed, and agonising pains in the head. Many of the victims were already _in extremis_, several died even while the doctor was examining them, and in the course of a few hours practically everyone attacked by the disease had succumbed. The only ones to recover were a few children, too young to give any useful information.

It would be useless to trace or describe the excitement which followed, even though the Press, at the instigation of the Government, was silent upon the matter. Help was rushed to Moorcrest, the dead were interred and the living helped in every way. The Ministry of Health sent down its most famous experts to investigate. One and all admitted that they were completely baffled.

On May 21st Ancoats was the scene of an appalling outbreak of the disease. People in the densely packed areas died like flies. But there were some remarkable circumstances which drew the attention of the trained observers who rushed to the spot to inquire into the phenomenon.

Ancoats had been the scene of the second explosion twelve days before. It was not long before a health official noticed the coincidence that the outbreaks at Moorcrest and Ancoats occurred exactly twelve days after the explosions in each place.

The coincidence was, of course, remarked upon as somewhat suspicious, but it was not until it was reproduced in the terrible outbreak at Nottingham that suspicion became a practical certainty. It was speedily confirmed by repeated outbreaks in other parts of the country. In each case the mysterious malady broke out exactly twelve days after the appearance of the violet vapour. In all cases the symptoms were precisely alike, and the percentage of deaths was appalling. Neither remedy nor palliative could be devised, and the best medical brains in the country confessed themselves baffled.

By this time there was no room for doubt that the terror was the deliberate work of some human fiend who had won a frightful secret from Nature's great laboratory. But who could it be, and what possible object could he have?

Leading scientific men of all nations poured in to England to help. For it was now recognised that civilisation as a whole was menaced; the fate of England to-day might be the fate of any other nation to-morrow. France and the United States sent important missions; even Russia and Germany were represented by famous bacteriologists and health experts. International jealousies and rivalries appeared to be laid aside, and even the secret service, most suspicious of rivals, began for once to co-operate and place at each other's disposal information which might prove useful in tracking down the author of the mysterious pestilence.

On the day of the meeting of the British Cabinet, two men and a pretty, dark-haired French girl were keenly discussing the terrible problem in a small but tastefully furnished flat in the Avenue Kleber, in Paris.

"I know only three people in the world with brains enough to carry the thing out," said the girl. "They are Ivan Petroff, the Russian; Paolo Caetani, the Italian, and Sebastian Gonzalez, the Spaniard. They are all three avowed anarchists, and, as we know, they are all chemists and bacteriologists of supreme ability. But I must say that there is not a scrap of evidence to connect either of them with this affair."

The speaker was Yvette Pasquet, and there was no one in whom Regnier, the astute head of the French Secret Service, placed more implicit confidence.

"If the doctors could settle whether this poisoning is chemical or bacteriological it would help us a great deal," said Dick Manton. "If it is chemical, I should be disposed to include Barakoff; he knows more about chemistry than all the others put together. But in any case, there is as yet nothing we can even begin to work on."

A fortnight went past. The death-roll in England had assumed terrible proportions, and apparently the authorities were as far off as ever from coming to grips with the mystery. But a clue came through the heroism of a London policeman.

One night Constable Jervis was patrolling a beat which led him through some tumbledown streets in the lowest quarter of Canning Town. Suddenly he caught sight of a man rushing from a small empty house. At once Jervis started in pursuit of the man, who was running hard away from him. As he did so, there came the sound of an explosion, and the house the man had just left collapsed like a pack of cards. At the same time the odour of the dreaded violet vapour completely filled the narrow street.

The Terror had attacked London, and Jervis knew that to cross that zone of vapour meant certain death.

He did not hesitate. Muffling his face with his pocket handkerchief as he ran, he dashed at full speed after the stranger, whom he could just discern. He crossed the zone of death, almost overpowered by the curious scent of petrol and musk that loaded the still air, and a moment later was in pursuit, blowing his whistle loudly as he ran. A moment later a second policeman, hearing his colleague's whistle, stood at the end of the road barring the way. The desperado was trapped.

Snatching out a revolver, the man backed against the wall and opened fire on his pursuers who were rapidly closing in on him. But both the policemen were armed, and both opened fire. Jervis's second shot killed the man on the spot.

He proved to be a well-known member of a Russian anarchist group which had its head-quarters in the slums of Soho. The gallant Jervis had faced certain death--as a matter of fact he was among the hundred or so victims when the epidemic broke out twelve days later--but he had done his duty in accordance with the splendid traditions of the force to which he belonged.

The source of the mysterious epidemic was now, to a certain extent, localised. It needed no great acumen to guess the motive and origin of the fiendish plot. But to discover the master-mind which held the full solution of the mystery was another matter.

The first step was a general round-up of known members of the Anarchist Party. They were arrested by dozens, and very soon practically all who were known were under lock and key.

To the intense surprise of the police, one and all acknowledged that they were fully familiar with the scheme. Many of them had actually taken part in its execution. The secret had been well kept!

The explosions, it was learned, were caused by small bombs about the size of an orange. These were placed in the selected houses and timed to explode in a few hours. Evidently there was some defect in the mechanism of the one sent to Canning Town, and the man who placed it there must have seen that it was likely to explode prematurely and rushed in panic from the house.

But of the source of the bombs one and all of the men professed complete ignorance. They were, it was asserted, received by post from different places on the Continent. It was evident that the crafty scoundrel at the head of the terrible organisation took elaborate precautions to prevent their sources of origin being discovered.

But to have traced the outbreak to Anarchist sources was a step of the first importance. Immediately every branch of the secret service of the western world was concentrated on the problem.

A hint from one of the men captured, who collapsed under the cross-examination to which the known leaders were subjected, put the police in possession of one of the bombs. It had arrived by post the day before, and the miscreant to whom it was sent was caught before he had time to make use of it.

It was now possible to prove definitely that the disease caused by the bombs was chemical in its origin. Upon analysis the powder with which the bomb was filled was found to consist of a series of, apparently, quite harmless chemicals. A small portion fired by the detonator found in the bomb gave off dense clouds of the pale-violet vapour, and animals exposed to it were speedily killed, exhibiting every symptom of the terrible disease. Unhappily the secret of the detonator used defied discovery. The one found in the bomb had been used in the only experiment that had been made, and too late it was discovered that no fulminating material known would explode the apparently harmless powder.

"That seems to narrow it down to Barakoff," said Dick Manton a few days later when Regnier brought them the news. "I don't think either of the others is equal to research work capable of producing such results. Do you know where Barakoff is now?" he asked in French.

Regnier shook his head.

"He was in Moscow a year ago," he replied, "and after that we heard of him in Prague, in Rome, and lastly in Madrid, but he disappeared suddenly and we have not been able to pick up his tracks again. He is a short, powerful, thickset man with a rather hunched back, but nothing else peculiar about his appearance."

Next day, however, Regnier came to the adventurous trio in great excitement.

"Barakoff is in England!" he declared. "We have just had word from Gaston Meunier who saw him in Brighton a week ago!"

"But how on earth did he get there?" asked Jules. "You know every one has been looking for him for months past. He could not possibly have got through by any of the ordinary routes."

"I'm as puzzled as you are, monsieur," was Regnier's reply.

"Well, if he is there we'd better go over," said Dick. "Yvette can go with me in Mohawk II and Jules by the night boat. I shall fly the Mohawk to my old shed in Norfolk; I have kept it on in case of emergency, and it is quite safe."

An hour later Dick was in close talk with a young Russian named Nicholas Fedoroff. He had been an active member of a circle of dangerous anarchists in Zurich, but had dropped out and was now living in Paris. By good fortune Dick had saved his baby girl, at imminent risk of his own life, from being killed by a motor-van in Paris, hence Fedoroff was impulsively grateful.

"Look here, Nicholas," said Dick bluntly. "I want you to tell me anything you can about Barakoff."

They were seated in a small cafe in the Rue Caumartin, which was Fedoroff's favourite haunt. The Russian glanced round fearfully.

"Hush!" he said in broken French and in evident horror. "I--I can't tell you! He has agents everywhere. If I were heard even speaking his name I should never get home."

The man's agitation was so pronounced that one or two men in the cafe glanced at him curiously. Dick saw that the mere mention of Barakoff's name had thrown the Russian completely off his balance.

"Come to my flat," he said quietly, "you have got to tell me."

They drove in a taxi to Dick's flat, where a stiff dose of brandy pulled the Russian together. Yet he still trembled like a leaf.

"How did you know that I knew Barakoff?" he asked.

Instantly Dick was keenly on the alert. He had no idea that Fedoroff had been associated with the notorious criminal; his appeal to Fedoroff had been a chance shot. Evidently he had stumbled on a matter of importance. But he was quick to take advantage of his good luck.

"Never mind how," he said. "I do know, and that's enough. You have got to tell me. I believe Barakoff is at the bottom of the trouble in England. I know he is there, and I want to know where he is and how he got there."

The Russian's agitation increased.

"You must not ask me; I cannot tell you," he gasped.

"Then a few words from me in a certain quarter--not the police," Dick suggested.

The Russian collapsed.

"No, no, I will tell you," he moaned. "He is in England, but I don't know where. He flew over."

"Flew over!" echoed Dick in utter amazement. "Nonsense, he couldn't have got in that way. Every aerodrome in England has been watched for months."

"But he did," the Russian asserted. "He has his own aeroplane. It makes no noise, and it goes straight up and down."

Here was a surprise indeed! The secret of the helicopter with its almost unlimited power for evil was also in the hands of one of the most desperate ruffians in the world! There was indeed no time to be lost.

Fedoroff could tell Dick little more. What the secret of Barakoff's influence over him was Dick could not fathom. He would say nothing, but evidently was in deadly fear.

One little item Dick did indeed extract and it was to prove valuable. Fedoroff knew that Barakoff had associates in Soho. And that was the only clue they could gain to his possible whereabouts.

That evening Dick, Yvette, and Jules crossed to England, and with official introductions from Regnier, Dick lost no time in getting into communication with Detective Inspector Buckhurst, one of the ablest men of Scotland Yard's famous "Special Department," a man whose knowledge of the alien scum which infested London was unrivalled. To him Dick told all he knew.

Buckhurst looked grave.

"I know of the man, of course," he said, "but I have never seen him and I don't think any of my men have. We have combed Soho out pretty thoroughly, but no one answering to Barakoff's description has been seen."

The position was very grave. If Fedoroff's information was correct--and Dick saw no reason to doubt it--here was a desperate scoundrel lurking in England armed with an aeroplane of unknown design and power, and in possession of a terrible secret which, unless his career was brought to an end, threatened the entire population of the country. But where was he hiding, and, above all, where was his machine? Could it possibly be hidden, Dick wondered, in the very heart of London? The idea was almost incredible, but Dick knew Barakoff's undoubted genius and his amazing daring.

A remarkable feature of Yvette's personality was her wonderful influence over children. They seemed literally to worship her. She would get into conversation with the half-tamed _gamins_ of the streets and in a few hours they would be her devoted slaves. She now proceeded to enlist the ragged battalions of Soho in a fashion that caused Buckhurst much amusement.

"Find out for me all the hunchbacked men you can," was all the instructions she gave them.

"But, mademoiselle," said Inspector Buckhurst, "it will be the talk of Soho, and our man if he is there will slip away."

Yvette was unmoved.

"Just think a minute," she said. "Who can go about all day and all night without being suspected? The children. Who can go into dens where your men hardly dare to venture? The children. Who know all the hidden haunts of which your men are utterly ignorant? The children. And finally, who are the most secretive people in the world? Again the children. Do not fear, Monsieur Buckhurst, they will not talk except among themselves, and that will do no harm."

Buckhurst was far from satisfied, but he had gained such a respect for Yvette that he did not venture to override her. At the same time, he told her plainly that he should keep his own men busy. Yvette only laughed.

During the next forty-eight hours dozens of hunchbacked men were reported. Many of them were people whom not even the police knew. They were, of course, mostly harmless, but Buckhurst opened his eyes when one of them proved to be a notorious forger for whom the police had been looking for some months, and who had all the time been hidden under their very noses! Buckhurst began to feel a growing respect for the amazing French girl, who had beaten his smartest detectives on their own ground. But, unfortunately, none of the hunchbacks was the man they wanted, and at last they began to suspect that Fedoroff's information was at fault.

Then came a dramatic surprise. One of Yvette's small assistants, a sharp little Polish Jew boy, came to her with a strange story. He had been wandering about the night before and had seen a hunchbacked man let himself out of the side door of a big building half-way between Greek Street and War dour Street. The man had walked a considerable distance in a northerly direction into a part of London the boy did not know at all, and had entered an unoccupied house, stayed a few minutes, and come out again. The lad had shadowed him all the way, and had followed him homewards, until he again entered the building in Soho.

Dick, Jules, and Yvette turned out at once. The boy pointed out the building to them. It was a tall structure which dominated all the others in the vicinity. It was apparently a big shop with storerooms above. On the facia over the windows was the name "Marcel Deloitte, Antique Furniture." There was nothing to indicate that it differed in the slightest degree from dozens of other shops and buildings in the neighbourhood. Yet Dick felt suspicious.

"We can do nothing till I get the Mohawk handy," said Dick. "I will bring her down to-night."

And he paused.

"I wish you would keep out of this, Yvette," he went on wistfully. "It is going to be very dangerous, I am convinced." The French girl was growing very dear to him, and he shuddered at the idea of her being mixed up in the coming struggle with a desperado of Barakoff's type.

But Yvette shook her head.

"I'm in this to the finish, Dick," was all she said in her pretty broken English, and Dick knew he could not move her. But he was full of fear.

That afternoon another explosion of the pale-violet vapour occurred in North London not far from Finsbury Park Station. Dick rushed to the spot with the boy who had followed the hunchbacked man, and the lad recognised the place without hesitation. The house destroyed was, he was confident, the one the hunchback had entered the night before.

Barakoff was located at last! But how was he to be captured? The problem was not so easy.

It was vital that, if possible, he should be taken alive. They knew what would follow the explosion at Finsbury Park, and there was a chance at least that if Barakoff were captured the secret of the disease, and possibly the antidote, might be wrung from him. If they could succeed in that hundreds of lives would be saved.

Together the three worked out a careful plan for the _coup_ they intended to bring off next morning.

Very early a dozen street arabs were playing innocently close to the two entrances of the mysterious building. They were chosen specimens of Yvette's band of ragamuffin detectives, and she knew that if Barakoff tried to escape he would have no chance of eluding their keen eyes. All the approaches were blocked by detectives, but Yvette insisted that none should approach the house itself. It was essential to the success of their plan that Barakoff's suspicions should not be aroused.

From the roof of a big building half a mile away, Dick made a careful examination of what he was now convinced was Barakoff's hiding-place. But he could see little. The roof was flat, but it was surrounded by a parapet practically breast high. There was obviously plenty of room to conceal a small aeroplane, but Dick could see nothing.

Dick and Buckhurst together saw the proprietor of the building from which Dick had made his observations. He readily consented to Dick's plan, and towards evening placed a trusty commissionaire at the foot of the flight of steps leading to the roof with instructions that no one was to pass on any account whatever. Soon after dark the Mohawk dropped silently on to the flat roof. They were ready now to catch their bird!

In the morning Yvette, under the pretence of wishing to buy some old furniture, entered the shop. So far as she could see there was nothing suspicious. There was a manager, evidently a Russian, and two assistants.

Asking for a Jacobean chest which she did not see in the shop, Yvette was at length invited to the upper floors. These she found to be full of furniture.

Climbing the stairs to the third floor, accompanied by the manager, Yvette found herself in a large room divided in the centre by a wall, and with a door in the middle. Opening this door the manager bowed to her to precede him, and Yvette, quite unsuspectingly, obeyed. Next second the door crashed to, and she heard a key turn in the lock. She was trapped!

Before she could recover from her astonishment there was a rush of feet behind her, and she found herself seized in a grip which, as she at once recognised, it was far beyond her strength to shake off. She struggled frantically, but in vain. She was hopelessly overpowered and swiftly bound, and laid, gagged and helpless, on a sofa in the corner of the room. Then for the first time she caught sight of her captor. She recognised him at once. It was Barakoff himself! _Worse still, he knew her_!

The man was mad with rage, his face convulsed and his eyes blazing with fury.

"So, Mademoiselle Pasquet! We meet at last!" he snarled, stooping over her until his face was within a foot of her own and she could feel his hot breath upon her cheek. "But it is for the first--and last time!"

Accustomed as she was to danger in many forms, Yvette could not repress a shudder. In the power of a ruffian like Barakoff! She knew, of course, that at any moment Jules might become suspicious of her long absence and come in search of her. But how long would he be and what might happen in the meantime?

Barakoff set swiftly to work and fixed inside the doors heavy bars which, as Yvette realised with a sinking heart, would effectually shut out anyone trying to gain admittance, until either the door was reduced to splinters or a hole was knocked in the wall. Then he picked her up without an effort and carried her into the adjoining room. This, to Yvette's intense surprise, was elaborately fitted up as a chemical laboratory, with all kinds of strange instruments and apparatus. It was evident that it had long been used for this purpose.

With an evil sneer Barakoff took from a cupboard what Yvette had no difficulty in recognising as one of the poison bombs! This he placed on a table and attached to it a short length of fuse. Then he began to busy himself with what seemed to be preparations for leaving, packing a few articles of clothing in a small bag and laying it down with a heavy coat beside it.

"When night comes, I go," he said. "But you--you will remain. But I shall leave you in good company, mademoiselle," and he pointed to the deadly bomb. "You will not feel dull. And after I am gone you will die--very slowly--of the twisted arms."

For a few minutes the miscreant sat silent, smoking a cigarette and regarding Yvette with a look of triumph she found even harder to bear than the consciousness of her terrible danger.

Jules, on watch below, had at length become uneasy. He entered the shop and asked one of the assistants if the lady was still there.

"Yes," replied the fellow readily, "she is upstairs with the manager looking at some furniture."

Jules, his hand on his pistol in his pocket, and feeling strangely uneasy, started up the stairs. There was no one in the building. What could have become of Yvette and the manager?

On the third floor he noticed the door through which Yvette had gone. He seized the handle and tried to open it. But the door was locked and there was no key.

Not daring to raise an alarm for fear of the consequences to Yvette, Jules hastened down the stairs, and signalled to one of the Scotland Yard men. In a low voice Jules told him what had happened.

"We must be ready to break down that door at once," he said.

With swift efficiency help was summoned, including a couple of men of the salvage corps, armed with powerful axes which would make short work of any ordinary door.

While the shop assistants were kept under surveillance, Jules and his helpers mounted to the third floor. They tried the door, and knocked. There was no reply, but inside they heard the hasty scurry of feet.

"Break it down," said Inspector Buckhurst, who had been one of the first to arrive.

The salvage men sprang forward, and one on each side of the door began a furious attack with their axes.

Instantly a shot rang out. Splinters flew in showers, but the door, heavily barred and plated with iron, for a time defied all their efforts. At last it gave way, and headed by Jules the police party rushed in.

Their first discovery was Yvette, lying unconscious and bleeding profusely from a wound in the shoulder. Barakoff had fired at her as he hurried from the room when the thunderous attack on the door began. But in his blind haste his aim had been bad, even at such short range, and she escaped with comparatively slight injury.

But where was Barakoff?

Rushing out on to the flat roof Jules looked hurriedly round. To the southward a queer-looking aeroplane was just vanishing into the thin mist. But behind it, going "all out," sped the Mohawk in furious pursuit. Dick Manton was taking a hand in the game of which he was a master! There could be but one end to that, Jules thought, with a sigh of relief as he turned to look after Yvette.

She was recovering consciousness and they were just about to carry her out, when one of the policemen with a loud cry dashed to the table. He had caught sight of a thin thread of smoke rising from the fuse of the bomb!

Luckily he was an old bombing instructor and knew what to do. A moment later the fuse was cut and the bomb's detonator removed. It was harmless now. Half a minute later it would have exploded.

Watching keenly from his roof Dick Manton had seen Barakoff's aeroplane rise swiftly and silently into the air. He had some slight trouble in starting the Mohawk, and the Russian was a mile away before the Englishman had started in pursuit.

Crouched in the driving seat of the Mohawk, Dick kept his eyes glued on the machine in front. He soon realised, to his dismay, that the Russian machine was much the faster and was leaving him behind. By the time they had gone ten miles and were out over the open country, he could only just discern the fugitive as a mere speck in the distance, and he realised with a sinking heart that a fleck of mist would enable Barakoff to escape.

Suddenly he discovered that the Russian machine had descended very low. A moment later it appeared to rise vertically, going up to a great height.

Instantly Dick followed and to his surprise found himself gaining rapidly. Then the Russian seemed to slip ahead again.

Several times this was repeated, and Dick at length divined the reason. The Russian could not run his elevating and driving propellers simultaneously. He travelled in a series of swoops, coming down very slowly as the machine drove forward, and then being compelled to stop the driving propellers while he gained the necessary height to continue his flight. No doubt this was explained by the fact that the planes were too small to keep the machine up without the elevating propellers.

Dick saw that he held a big advantage. The Mohawk, though slightly slower, could rise and go forward at the same time under the influence of both propellers.

As they sped over Kent, Dick began to realise with joy that he was gaining. Slowly the poison-fiend began to come back to him.

Then came the critical moment. Five hundred yards ahead and a thousand feet below, Barakoff, close to the ground, must rise soon to gain the elevation he required.

That was the moment for which Dick had been waiting. He called on his machine for the last ounce of effort he had been holding in reserve.

The Mohawk shot forward. A few seconds later Dick was directly above the Russian. So far as air tactics went he had won; the Russian was entirely at his mercy.

Then began surely the strangest aerial combat ever witnessed. To and fro the machines dodged, Barakoff striving to gain height and succeeding for a moment only to find his pursuer above him again and bullets whining round him; Dick striving to force the Russian down to the ground where he must either land or crash. For fully half an hour the machines flitted backwards and forwards around the town of Ashford. Dick had no fear of the result; his only risk was whether he could send Barakoff down before dusk came. Unless he could do this there was every danger that the Russian would escape under cover of darkness.

At last the end came.

Dick had forced his antagonist so low that, as a last desperate resort, Barakoff had to leap upward to clear a big group of elms. He miscalculated by a few feet, his machine touched the upper branches and went smashing to earth. Three minutes later Dick was standing beside the body of the death-dealer.

Barakoff's machine was a complete wreck and was blazing furiously. The man himself had been flung clear and lay in a crumpled heap, stone dead.

There is little more to tell.

The formula for the powder with which the bomb was charged was found in Barakoff's laboratory, and with it, in Russian, a prescription which, on being tested, proved to be a complete cure for the disease. It was found just in time to save those who would otherwise have been the victims of the explosion at Finsbury Park.

It was evident that Barakoff must have maintained his laboratory in Soho for months. Obviously the manager of the shop was one of his accomplices, and apparently he had recognised Yvette and deliberately thrown her into Barakoff's hands. Then realising that discovery was inevitable he had slipped out of the building, probably by a window as neither of the assistants had noticed him leave. He was never found. The assistants themselves proved to be respectable young fellows who had been employed only a few weeks and who clearly knew nothing of the nefarious conspiracy.

Nothing but the Mohawk had prevented Barakoff's escape! And Dick Manton received later on the official thanks of the British Government for his daring exploit.

CHAPTER FIVE.

THE MASTER ATOM.

"Oh! la la! How horribly dull life is! I do wish something really startling would happen, Dick!"

The words were spoken in pretty broken English by Yvette Pasquet, who, charming and _chic_, as usual, was sitting with Jules and Dick Manton. The adventurous trio were dining _al fresco_ in the leafy garden of the old-world "Hotel de France" on the river bank at Montigny, that delightful spot on the outskirts of the great Forest of Fontainebleau, a spot beloved by all the artists and _litterateurs_ of Paris.

"Something will happen suddenly, no doubt," Dick laughed, glancing at his beloved. "It always does!"

"I sincerely hope it will," declared Jules in good English. "We're really getting rather rusty. I met Regnier yesterday out at Pre Catalan with Madame Sohet, and he hinted to me that some great mystery had arisen; but he would tell me nothing further."

"Regnier, as head of the Service, is always well informed, and like an oyster," Yvette remarked with a laugh. "So I suppose we must wait for something to happen. I hate to be idle."

"Yes. Something will surely happen very shortly," said Dick. "I have a curious intuition that we shall very soon be away again on another mission. My intuition never fails me."

Dick Manton's words were prophetic, for on that same evening before a meeting of the Royal Society in London, Professor Rudford, the world-famed scientist, made an amazing speech in which he said:

"Could we but solve the problem of releasing and controlling the mighty forces locked up in this piece of chalk, we should have power enough to drive the biggest liner to New York and back. We should have at our disposal energy unlimited. The daily work of the world would be reduced to a few minutes' tending of automatic machinery. And, I may add, the first nation to solve that problem will have the entire world at its mercy. For no nation, or combination of nations, could stand even against a small people armed with force unlimited and terrible. And-- gentlemen--_we are on the way to solving that problem_!"

As the words fell slowly and calmly from his lips his hearers felt a thrill of ungovernable emotion, almost of apprehension. For they knew well that he spoke only of what he knew, and the measured phrases conjured up in their keen brains not only a picture of a world where labour had been reduced to the vanishing point, but of a world where evil still strove with good, where the enemies of society still strove against the established order of things which they hated, where crime in the hands of the master criminal, armed with force whose potentiality they could only dream of, would be something transcending in sheer horror all the past experiences of tortured humanity.

Supposing the great secret _fell into the wrong hands_!

The speech at the Royal Society was a nine days' wonder.

The unthinking Press made merry in the bare idea of a lump of chalk being a source of power. Then the transient impression faded as public attention returned to football and the latest prize-fight. But behind the scenes, in a hundred laboratories, students bent unceasingly over their myriad experiments, striving to wrest from Nature her greatest secret, the mystery of the mighty energy of the atom. Since the day when Madame Curie had discovered that in breaking up, yet seemingly never growing less, radium was shooting off day and night power which never seemed to diminish, the minds of the men of science had been filled with the dream of discovering the secret.

Could they learn to accelerate the process? Could they induce radium to deliver in a few moments the power which, expending itself for centuries untold, never seemed to grow less? Could they learn to control it, or would it, when at last the secret was discovered, prove to be a Frankenstein monster of titanic power, wreaking untold destruction on the world?

A thin, keen-faced man sat facing the British Prime Minister in his private room in Downing Street a few days later. This was Clinton Scott, one of the smartest men of the British Secret Service, a man of wide culture and uncanny knowledge of the underworld of international crime. His profession was the detection of crime; his hobby science in any form.

"We have very disturbing news, Scott," said the Prime Minister, "and I have sent for you because the problem before us is largely of a scientific nature and I know all about your hobby."

Clinton Scott smiled.

"You are aware, of course, of the latest developments in the search for some method of releasing and controlling atomic forces," went on the Prime Minister. "I do not profess to understand them deeply myself, but I have a general idea of what is being done and what success would imply. Professor Rudford, to whom I applied for information on the subject, tells me that such a discovery would revolutionise world conditions. You will understand of your own knowledge all that it implies, and that is why I have sent specially for you in this matter."

"I am at the country's service," replied Scott.

"Now information we have received from Norway suggests very strongly that the problem has been solved," the other said. "We have no details--nothing in fact very definite at all. But it is certain that some very queer things have been happening. And from what Professor Rudford tells me I am assured that we cannot afford to neglect them. Our ordinary men are useless for this kind of thing. Men with a considerable knowledge of scientific subjects are absolutely necessary. Otherwise matter which, properly understood, would be full of significance will be passed over as of no account and quite minor and unessential incidents will be followed up, and there would be serious waste of time. And time is valuable."

"I agree that it is," was the terse reply.

"I want you to go to Norway and look into the matter," the Prime Minister went on. "Of course I will see that you get all the information we have, and you can select your own assistants."

Clinton Scott suddenly looked grave.

"Is it known at all?" he asked. "Who is behind this--I mean who has made this discovery? You will appreciate my reason for asking. If it is the work of a genuine man of science there would be no immediate danger, though of course such an invention would upset all ideas of international relations. It is literally true, as no doubt Professor Rudford will have told you, that the nation in exclusive possession of such a secret could dominate the world. But there are one or two men in the world who, with such a secret in their possession, would be a real peril to civilisation."

"Do you know a man named Lenart Gronvold?" asked the Premier.

Clinton Scott started visibly.

"Do you mean to say he is in it?" he gasped in utter astonishment.

It was the Premier's turn to be surprised.

"Why--who is he?" he asked. "Professor Rudford had never even heard his name and laughed when I suggested that he could have had anything to do with it."

"He won't laugh when he gets some real idea of Gronvold's ability," said Scott bitterly. "The man is one of the mysteries of the world of crime," he went on. "Exactly who he is we don't know--I mean we know little about his life. But we believe he is Norwegian born, though he has strong Russian characteristics. We know he studied at Leipzig. Tutors who knew him well speak with the utmost admiration of his amazing brain power as a student and the daring of his conceptions. But for some reason he never did well in examinations and attracted no attention whatever outside a very limited circle. Personally, I believe that for some strange reason he deliberately elected not to call attention to himself, for there is not the slightest doubt that he could with ease have captured every honour the University had to bestow. After leaving Leipzig he disappeared for some years. I don't know how he spent them. But I do know that he is a chemist of amazing ability. He has, moreover, been mixed up with a number of puzzling international crimes, though we have never been able to bring any of them home to him. Do you remember the big bank robbery at Liverpool three years ago?"

The Premier nodded.

"You mean," he said, "when the bank vaults were blown open with dynamite and half a million in gold stolen?"

"That's the case," said Scott. "Only it wasn't dynamite, there was no explosion. The thick steel and stone walls of the vaulted safe had been melted through as if they had been butter. The story of an explosion was deliberately given out to deceive the thieves. But the fact is that some process was used of which we have no knowledge whatever."

And he paused, then went on:

"Now I am pretty sure Gronvold was in that. I was called in before anything had been touched. And in one corner I picked up a scrap of paper bearing some queer formulae of which I could make nothing. It had evidently been dropped by accident. And it bore Gronvold's name. Moreover, as I ascertained by a visit to Leipzig, where I saw some of the old University registers, it was in his handwriting. But where he is, how he got into England, how the burglary was effected and how he got away with such an enormous weight of gold we never could make out. If he is really in this new discovery we are face to face with a terrible problem. The man is absolutely without scruple, and for three years he has had the use of half a million of money for his experiments. He may have done anything in that time."

"But how did you know of him?" asked the Premier.

"It's a queer story," replied the other. "Simmons, one of our men in Christiansand came across, quite by accident, a drunken Norwegian sailor who told a strange story of the blowing up of a mountain by a tiny cartridge placed at the bottom of an old mine shaft. He actually mentioned Gronvold's name, and claimed to have been one of his assistants. When he became sober he was evidently terribly alarmed at having talked, and denied the whole story. The same day he disappeared, and Simmons has been unable to trace him."

He went on after a pause:

"Now the blowing up of a mountain is a fact. A hill nearly a thousand feet high in a wild lonely district north-east of Tonstad has absolutely disappeared--levelled out. To have done the work by ordinary means would have meant years of labour and would have cost a fortune. There can be no doubt that some entirely new force has been employed. Officially the occurrence is attributed to a landslide; actually it is and can be nothing of the kind. Now this, coupled with what the Norwegian sailor said, suggests that we ought to look into the matter. Whether the Norwegian Government knows anything about it I do not know, and the matter would be of such importance from the international point of view that we cannot make direct inquiries."

"Will you take it in hand?" asked the Premier. "Whom will you get to help you? I am afraid the ordinary men would be of very little use."

"I think I will run over to Paris and see Regnier," replied Scott. "He has a fellow named Manton who will certainly be useful. He was in our flying corps and was invalided out owing to wounds. He has done some wonderful work and has an entirely new type of aeroplane which he invented and which, by the way, our people would have nothing to do with. Regnier swears by him. He works always with a French girl named Yvette Pasquet, who did some splendid intelligence work during the war, and her brother Jules. They will have nothing to do with anyone else when they are on a case, and they have had some amazing results."

Crossing to Paris by the afternoon air express Scott the same evening was warmly greeted by Regnier. He rapidly explained his visit. Regnier looked grave.

"I have heard of the man," he said, "but have never seen him, I don't think in a case like this you can do better than Manton. He is very well up in all these scientific things; they seem to be a perfect craze with him."

An hour later, Regnier, Scott, Dick Manton, Yvette, and Jules were closely discussing the problem in Manton's rooms.

"We have got to find that sailor," was Dick's verdict, "and luck is going to have a good deal to do with it. I suppose Simmons is on the look out for him?"

"Yes," replied Scott, "I wired him at once."

"Do you think Gronvold and the sailor have quarrelled?" put in Yvette.

"I think not," was Scott's reply. "If they had there seems no reason for the man's alarm. I think he calculated on going back to him. That was Simmons' view, too."

Dick, who had been carefully studying a map, looked up.

"Just look here," he said, "you could hide an army in this place."

The map was in contour and gave a vivid impression of the wild and desolate country, a broken mass of hills and lakes, stretching north and east from Tonstad.

"Suppose Gronvold is there," said Dick, "he could hide anything he wanted to. I don't think he would have travelled far from its base to blow up the hill--that was probably experimental. My idea is that he has established his laboratory somewhere in the hills about there. There is no population and little or no traffic through the district. He must send to one of the towns for supplies, and Christiansand is the most likely. I should guess that the sailor had come there for that purpose and may come again."

"He did not leave the town by boat," declared Scott. "Simmons made the most careful inquiries on all the boats in the harbour and no one of his description was seen."

Three tourists a week later were lodged in a comfortable hotel in the Dronningens Gade, one of the principal streets in the busy port of Christiansand. They were Yvette, Jules, and Scott. Dick had flown the Mohawk direct to the wild district north-east of Tonstad, and with the help of a light tent had pitched a camp in a little wood a couple of miles from the southern edge of the blown-up hill. He had taken pains in the selection of a suitable place and his camp and the Mohawk were so admirably hidden that they were safe from discovery, unless some one actually walked right up to them, a contingency which in that roadless, unpopulated country was extremely unlikely. But though hidden himself he commanded a wide view.

For two days Dick devoted himself to a thorough examination of the surrounding country, quartering it thoroughly either on foot or in the Mohawk. He could however see nothing in the least suspicious.

Then came a surprise.

His only method of receiving news from the others was to "listen in" on the wireless telegraph set with which the Mohawk was fitted for messages which, directed to an address in England, were handed to the Christiansand radio station for dispatch, but were really intended for him. These messages were handed in at eight o'clock precisely and Dick usually got them within half an hour.

On the third day of his watch came the message:

"Sailor located. Travelling north with pack mules. We follow. Osterluis road."

The man, as he was to learn later, had been spotted by Yvette in Christiansand. She had seen him leave a small cafe much frequented by sailors, and had been struck by his likeness to the description given by Simmons. She had followed him for some time while he made a variety of purchases at numerous shops, and had been struck by the fact that a mere sailor should evidently have such a large sum of money at his disposal. Luckily she had encountered Simmons, who at once recognised the man and had promptly disappeared to avoid arousing his suspicions.

Yvette was able to learn that all the man's purchases were being delivered to a small inn on the outskirts of the town, and a few inquiries showed that he had four mules stationed there.

The matter began now to clear up. They were sure of the man; at least he could not leave without his mules and stores. Jules and Scott took up the watch at the inn, while Yvette shadowed the suspect. It was thought best that Simmons should not appear. It soon became evident that the man had no associates in Christiansand. All he did was to visit shops, paying cash for all his purchases and having them sent to the inn where his mules were stabled.

The next day, with his mules heavily loaded, he set out from Christiansand, taking the road to Trygstand and Ostersluis.

Yvette, Jules, and Scott decided to follow him on foot. To have taken horses would have told him he was being followed as soon as he left the road, as they were pretty sure he would, sooner or later. Luckily all three were splendid walkers and felt they would have no trouble in keeping up with the heavily-laden mules. Cramming a few necessities into rucksacks they were soon on the track of their quarry.

Man and mules made steady progress. They were soon through Trygstand and, shortly after, caught sight of the Mohawk high above them and evidently following the road on the watch for them.

With a handkerchief tied to a stick Yvette swiftly signalled to Dick the brief facts, and the Mohawk passed on towards Christiansand. When the sailor and the mules were hidden in a dip in the road Dick landed, and all four held a brief consultation as to their future plans.

As a result Scott put on his best speed and soon passed the sailor who had stopped for a rest. The man was now between two parties on the ground and under observation from Dick from the air. He certainly could not escape.

A few miles beyond Trygstand he suddenly left the high road, and turned westward and north across the open country. Evidently he was not bound for Ostersluis. But where could he be going? For miles there was not even a house in the deserted track of country into which he had plunged.

But it was evident he knew his bearings thoroughly. Hour after hour he jogged along, and soon the pursuers realised that they had been wise not to bring horses. No horse could have crossed the country over which the sure-footed mules went swiftly without a stagger.

At nightfall the man camped. Apparently he paid no attention to the passing of the aeroplane, for he barely glanced at it. Building a small fire under the shelter of a rock, the three pursuers spent a comfortless night. Dick had flown to his camp, intending to pick the party up again at dawn.

Early next morning the man was afoot and continued his journey. He was now in the wild country well to the west of Ostersluis, and travelling due north. Yvette, Jules, and Scott were a mile behind, following with the utmost care not to reveal their presence and so rouse the man's suspicions.

They had gone but a few miles when the man paused on the flat top of a high hill, which on the side away from them sloped steeply into a deep gorge at the foot of which ran a small stream. They watched him narrowly.

With great care he got the four mules together, standing side by side. He himself took up a position directly in front of them and almost touching the animals' heads.

A moment later man and mules sank together, apparently into the earth and disappeared!

They could hardly believe their eyes! Surely the man must have gone down the reverse slope of the hill. But they were confident that he had not moved.

They hurried to the spot. Not a sign of any living thing was to be seen! The mystery was profound.

While they stood gazing at one another in speechless amazement, the Mohawk, which they had not perceived above them, dropped vertically downwards and landed a few yards away. Dick sprang out.

"Did you see?" he gasped. "The man and mules went down into some sort of pit. But where was it?"

The flat top of the hill was broken into a series of narrow cracks; apparently the rock of which it was composed was of volcanic origin. They examined it closely, but they could discover nothing which offered a solution of the mystery.

Dick described closely what he had seen from the sky. It agreed with what the others had observed. The man had got the mules together, and all had sunk slowly downward. Dick had seen the black mouth of the pit for a few moments and a blaze of light. Then the pit had disappeared, and the ground resumed its normal appearance.

"We shall have to camp here to-night," said Dick. "We must get to the bottom of this. We shall have to take turns to watch. In the meantime we had better have a look round."

Having closely examined the top of the hill, they turned to the deep gorge and descended to the bottom. The stream, they found, issued from the hill itself, flowing out from a low tunnel high enough to admit the passage of a man. From it also issued a cloud of mist which spread over the bottom of the little valley in a thick blanket which completely concealed the surface of the ground from anyone at the top of the hill.

But still more remarkable was that the bed of the little stream was deeply covered with what appeared to be recently melted lava. In many places it was still hot, and the water, they found, was nearly boiling. The first traces of this were found at the mouth of the tunnel from which the stream emerged, and for hundreds of yards the molten rock could be traced, as though it had poured from the tunnel and flowed down the bed of the brook.

Wood and water were available in abundance, and soon they had pitched their camp, near enough to the top of the mysterious hill to enable them to watch it closely and yet well concealed so that if the man reappeared they would have no difficulty in escaping observation.

The first watch fell to Yvette, and with a revolver ready for instant use, she prepared to spend a couple of lonely hours on the edge of the hill. The camp was but a quarter of a mile away so that a shot would bring her speedy help at any time.

A brilliant moon lit up the country for miles.

There was no trace of any living thing. Everything was still and silent.

Yvette had been on watch about an hour when she became aware that the air was full of a dull murmur of sound. She listened intently. There was no mistake about it. A dull throbbing noise was distinctly discernible.

She walked round the flat top of the hill, looking keenly in every direction and trying to locate the position from which the mysterious sound was coming. But it was in vain.

Glancing into the gorge, she saw a strange and terrible phenomenon. The course of the little brook was traced in a dull fiery glow. Clouds of steam were rising thickly into the night air; she could plainly hear the sharp hiss of water on something hot.

She ran swiftly down the hill. At the bottom she paused on the edge of the stream. The water had disappeared and in its place ran a river of molten rock! Through her boots she felt the heat of the ground.

Returning to the top of the hill she waited for Dick, who was now almost due to relieve her. In a few moments he appeared and listened in amazement as she gasped out her story.

The dull, throbbing noise was still audible.

"Machinery," said Dick laconically, "but where?"

Suddenly he flung himself on his face, and pressed his ear close to the ground.

"Listen," he said.

Yvette followed his example. There could be no mistake; the mysterious sound was coming from the ground beneath their feet! The earth was full of muffled thunder.

Dick took from his pocket a hammer and struck a sharp blow on the flat rock beneath their feet. It rang hollow! Unmistakably they were standing on the roof of a cavern.

Walking to the camp they roused the others and told them what they had seen and heard.

"We have got to catch that sailor if we wait here a month," said Scott. "He must come out again some time. But how about food?"

"We have enough tinned stuff in the Mohawk for a week," said Dick, "so we shall be all right for a few days. In the meantime we must watch the place closely."

Next day passed without incident until evening was drawing on. Then Yvette, who was watching the top of the hill while the others rested, at six o'clock gave a low whistle. She was lying on the ground keeping observation between a couple of rocks which hid her completely. In a moment the others had crawled to her side.

"Look!" she said.

On the top of the hill, three hundred yards away, stood the sailor and the four mules, clearly silhouetted against the evening glow. He had appeared suddenly, Yvette told them, just on the spot where he had disappeared on the previous day.

"We must get him," said Dick.

The man with the mules started to return along the way he had come. They saw at once that the path he was taking would bring him close to them.

With the mules unloaded the man evidently had no intention of walking. He mounted one of the animals and rode towards them at a fast trot.

He was within twenty yards when Dick aimed his revolver and fired. The mule the man was riding bolted, throwing its rider heavily. Before he could recover himself he was bound and helpless. The other three mules stampeded wildly and were soon out of sight.

Carried to the camp the man soon recovered. But he resolutely refused to say a word.

"Well," said Dick. "We must try to get into the cave. Perhaps the tunnel out of which the brook runs will lead us to it."

They were soon at the mouth of the strange tunnel. There was no sign of the molten matter of the previous night. The stream, thick with mud, flowed sluggishly, but the water was cool, and the ground, which the night before had been too hot to walk upon, was now not more than uncomfortably warm.

With Dick leading, Scott and Yvette next in order, and Jules bringing up the rear they entered the mouth of the tunnel. There was, they found, just room for them to pass, stooping low and walking knee deep in the little stream. They were, of course, in total darkness, for Dick was afraid to show a light for fear of betraying their presence.

For a hundred yards Dick groped his way onward. Then his outstretched hands struck something soft. It was a kind of curtain hung across the stream, thick and heavy.

Cautiously he slightly raised one corner and peered through. The sight that struck his eyes filled them with amazement.

They were at the entrance to an enormous chamber, a hundred and fifty yards across, dimly lighted by a single big electric lamp, the only one alight out of dozens which hung from the roof. The floor sloped steeply upwards at the far end where they could make out a kind of platform, reaching nearly to the roof and with steps leading downward into the great hall. All round the side were a series of openings, apparently small chambers cut into the solid rock. From one of these the stream they had followed seemed to issue, crossing the floor of the great cave in a narrow deep channel.

But what fascinated Dick's attention was a great table, apparently of iron, which occupied the centre of the cave. It was heavily constructed and seemed to be based on massive legs which went down into the rock. Upon it stood a strange machine unlike anything he had ever seen before and of the use of which he could not form the smallest idea. Surmounted by two huge governor balls, it was a complicated mass of polished wheels, of some metal which Dick could not identify, and which gleamed with a strange radiance in the light of the huge electric lamp overhead. From the machine a bewildering mass of wires led to a series of points at the face of the rock.

So much Dick could make out in the dim light. He was keenly anxious to learn more. But how was it to be done? No sign of any human being was to be seen, but he could not imagine that what lay before their eyes was the work of the solitary sailor who now lay bound in their camp.

At any rate they could not remain where they were. Dick decided to try to gain entrance to one of the wall chambers where they could shelter with a better chance of seeing what would happen in this underground home of mystery. But which should they choose?

Some of the chambers were half-way to the roof and were reached by steps cut in the solid rock. Dick decided on one of these not far from where they were standing. They crept cautiously from their hiding-place and stole along to the bottom of the cave. A moment later they were at the foot of the steps. These they hastily climbed, and soon found themselves in a fair-sized cave, fifteen or sixteen feet above the floor of the main cavern and commanding a good view of the entire area. It was dry and warm and formed an ideal post of observation, provided their presence remained undiscovered.

Suddenly a blaze of light struck their eyes. Some one had turned on the whole of the electric lamps which hung in clusters from the roof.

Peering cautiously out they saw, to their amazement, half a dozen men issue from different chambers near the floor of the cave. All wore big round spectacles of deep blue glass and were clothed in close-fitting garments of rubber, with heavy gauntletted gloves of the same material. Apparently they could not see well, for the spectacles must have been almost impervious to ordinary light.

One of the men, fixing his spectacles on more firmly and, drawing his rubber overall more closely around him, approached the strange machine which stood on the table. The others proceeded to the points at which the wires from the machine reached the side of the cave. Here they took up some kind of tool which looked like a gigantic blowpipe and stood ready as if awaiting a signal.

A low whistle sounded from the man at the table, as he grasped a small wheel and gave it a quick turn.

An instant later an appalling blaze of light burst from the strange machine, and the cave was filled with a roar of sound, a terrible deep drone of such frightful intensity that the hidden watchers shuddered as if with actual physical agony. Dick felt the sweat start suddenly from his forehead and pour down his face. Anxiously he glanced towards Yvette. She lay with her face buried in her arms, her body trembling convulsively. Scott and Jules, their faces white as chalk, were gazing at the unearthly light which streamed from the whirling machine, shading their eyes with their hands to shelter them from its blinding radiance. They could not look at it for more than a few seconds; it was like trying to gaze at the sun at midday.

Taking a letter from his pocket, Dick bored a tiny hole in it with his scarf pin. Through this hole he found he could see in comparative comfort. He signed to the others to do the same, and soon all four--for Yvette quickly recovered her self-possession--were eagerly watching the strange scene before them. Speech, in the deafening noise by which they were surrounded, was, of course, out of the question.

The man at the great table in the centre of the cavern evidently had a task of great difficulty to control the movements of the strange machine, which he seemed to do by means of a large wheel something like the steering wheel of a steamer. Long streamers of flame shot from it in all directions, and as its mass of wheels revolved at terrific speed it shook and trembled as if it would actually leap from the table.

In the meantime the men at the rock face were hard at work with big blowpipes, from the muzzles of which shot streams of fire of such intensity that the solid rock seemed to melt away like butter. The molten matter was led by ducts in the ground through a grid of some metal, evidently highly refractory to heat, for it appeared to do no more than glow white-hot even in the terrific temperature of the melted rock. After passing through this grid the molten matter was led to the bed of the stream, from which the water had in some manner been cut off, and flowed out the way Dick and his companions had entered.

What was the object of the work?

Dick could not guess, but every now and again one of the men would walk to the grid and with a long implement shaped like a hoe would scrape off something adhering to the bars, which he deposited in a big tank of water. Dick determined that, sooner or later, he would obtain a specimen.

But in the meantime their position was decidedly precarious. If they were observed there was no possible way of escape, for the tunnel by which they had entered was barred by the stream of molten matter. They could only lie still and hope that no one would enter the gallery in which they lay concealed.

After two hours of work, the man at the table stopped the machine, and all the men straightened out for a rest. Evidently they were very much exhausted. The lights were extinguished, except for the single one which was burning when they entered, and the men returned to their quarters, evidently almost falling with weariness. Dick came to the conclusion that they could only carry on the work on which they were engaged for a short time and that after that sleep and rest were imperative. The flow of molten metal had stopped and the water was again allowed to flow along its ordinary channel, from whence it sent up huge clouds of dense steam.

This gave Dick his chance.

Sending the others to the mouth of the exit, he cautiously crept towards the tank in which were deposited the scrapings from the grid which filtered the molten rock. He reached it safely, and plunging in his arm up to the shoulder, abstracted a couple of handfuls of what seemed like heavy shot. These he placed at once in his pocket.

He was about to return to the others when his attention was caught by the queer platform at the one end of the cave. Looking at this carefully he found that it was really a huge lift, and at once the mysterious disappearance of the sailor and the mules was explained. It was evident that the top of the lift was really the thin covering of rock which had sounded hollow when tapped and that this had been so cut that when the lift forced it into position only traces of ragged crevices were left on the surface. Dick could not but admire the ingenuity with which this approach to the subterranean retreat had been devised.

Presently he heard a heavy knocking above his head and, guessing the cause, shrank back for shelter into the mouth of a small cave adjoining. A moment later a man emerged from one of the other chambers and approached the lift. Dick was curious to see how it worked. There was, as he could see, a small electric motor fitted to it, but where could the necessary power come from?

The new-comer carried in his hand a tiny machine which was in every respect a duplicate in miniature of the big one on the central table. But it was so small that the man carried it easily in one hand. From it ran a pair of electric cables which the man proceeded to connect with the terminals of the motor.

Placing the machine on the ground he gave the wheel a sharp turn. Immediately the tiny machine began to revolve, throwing out flashes and flames exactly like the larger one but on a miniature scale.

Clearly, however, there was considerable power in it, for the lift at once commenced to descend. On it stood a man whom Dick instantly recognised as Gronvold. And he was accompanied by the sailor whom Dick had left safely tied up in their camp. Evidently Gronvold had found and released him.

Their position was now indeed one of terrible gravity.

As soon as the lift reached the bottom the two men stepped off and the lift reascended, moving upward with an ease which showed the tremendous power developed by the tiny machine. Here, indeed, was something of which Dick had had no previous experience.

The three men crossed the cave to the shelter occupied by the man who worked the big machine, who was evidently the captain, and Dick knew there was no time to be lost.

Directly the men entered the shelter, Dick dashed across the cave to join the others, snatching out his revolver as he ran.

He had nearly reached them, when a whistle blew and instantly half a dozen men rushed from different caves. They were discovered!

"Take care of Yvette, Jules!" Dick yelled as, with Scott at his side, he faced round to the men who were rushing at them from three sides.

Instantly Yvette and Jules plunged into the tunnel. Dick and Scott backed after them with drawn revolvers threatening the men in the cave.

For a moment the leaders hesitated; apparently they were not aimed. Then Gronvold rushed to the front, followed by the captain, both carrying curious weapons which looked like heavy pistols.

All four men fired simultaneously. Dick saw the captain drop, evidently shot dead, and heard a bullet whiz past him and strike the rock behind. A burst of flame singed his hair, and he felt the hot breath of it on his face.

Then Gronvold fired at Scott. The effect as the bullet struck him was strange and awful. His body actually disappeared in a mass of flame under the impact of some projectile of unimaginable power and energy. At the same instant Dick slipped on a projecting bit of rock and fell heavily on his head. As he lost consciousness he heard the crack of a revolver behind him. Yvette and Jules, hearing the shots, had returned in the nick of time. Jules snatched up Dick and carried him down the tunnel, while Yvette very coolly shot down Gronvold just as he was reloading his terrible weapon.

When Dick recovered his senses he found himself lying on the ground at the entrance to the tunnel, his head pillowed on Yvette's arm as she tried to pour some brandy between his lips. He could feel the sobs which shook her, and even felt a tear on his face. Jules stood on guard at the entrance to the tunnel, his revolver ready for instant action in case of pursuit.

As Dick opened his eyes, Yvette gave a gasp of relief.

"Oh, dearest, I thought you were dead!" she sobbed and burst into tears. A moment later she turned away blushing scarlet. She had betrayed her secret at last. And even in his confused state Dick felt a thrill of triumphant joy.

His head spinning he staggered to his feet. But he would have fallen if Yvette had not caught him.

"Sit down, Dick," she said peremptorily. "Jules can look after this place."

Dick obeyed, perforce; he was so sick and giddy that he could have done nothing even if the expected attack had come.

But it never came. Suddenly as they stood there, tense and waiting, a terrific convulsion shook the earth. With a terrible roar the great cavern collapsed and a vast burst of smoke and flame vomited to the sky, and a deep crater was left by the subsidence. Sick and dizzy, with showers of stones falling all around them, they stood aghast while explosion after explosion rent the air, rendering the crater deeper. It was some minutes before quiet reigned again and, white and shaken, after their nerve-racking experience, they were able to collect their shaken faculties and make an examination of the scene.

The hill beneath which the cavern was located had practically disappeared; in its place was left nothing but a heap of torn and tumbled earth and rock. Its dreadful secret was safe, for the cave and its contents, and the men who had wielded such titanic forces, were buried deep under tens of thousands of tons of debris.

Perhaps it was as well, Dick thought. There are some forms of knowledge which mortals ought not to possess; there are some powers which they are not fit to handle.

Whatever secret Gronvold had discovered, it rested with him for ever on the very scene of his ill-omened labours. What had gone wrong in the depths of the cavern they could not even imagine, but it was evident that the mysterious force which Gronvold had called into existence, whatever it was, had destroyed him and his companions. And it was almost by a miracle that Dick, Yvette, and Jules had escaped.

Slowly and painfully they made their way back to their camp, and for the first time Dick became conscious of the great weight of the double handful of shot which he had taken from the tank. He drew some of it out and examined it by the light of the fire. As he did so he gave a cry of surprise. For the "shot" was nothing more or less than tiny nuggets of virgin gold.

Here was an addition to the mystery. As Dick knew perfectly well, there was not an atom of gold-bearing rock within hundreds of miles of where they stood.

It was evident that one of the secrets of Gronvold's invention was that it gave him the power of actually bringing about the transmutation of substances. There was some element in the rock which was susceptible of being changed into gold by a process at which they could not even guess. But if this were so, Gronvold had indeed, as they suspected, been able to solve the problem of loosing the incredible force contained in the atom. His discovery was, as Dick at once realised, on the lines of the latest development of scientific thought.

Dick was to see the problem solved in later years by more reputable investigators.

But he could never forget his strange encounter with the wonderful but misguided genius whose career had been so terribly brought to an end by the dread power he had himself evoked.

CHAPTER SIX.

THE HORROR OF LOCKIE.

Many readers will recall the tragedy of Renstoke Castle and the terrible death of young Lord Renstoke. The case aroused much sensation at the time. It would have aroused far more had the real facts been allowed to transpire.

They were known, however, to only a few people, and, for reasons which were at the time sufficient, they were kept secret. I am now able to lift the veil which shrouded one of the most perplexing mysteries which has ever puzzled the scientific world. Even now, the story is not complete; the great secret died with the amazing but perverted genius who discovered it.

Lord Renstoke, a young man only thirty, was one of those favoured individuals on whom Fortune seemed to have showered all her gifts. Born and brought up in Canada, he was connected only very remotely with the ancient family of Renstoke, and no one ever dreamed that he could by any possibility succeed to the title, which carried with it Renstoke Castle and a rent-roll of something like a hundred thousand pounds a year.

James Mitchell, as Lord Renstoke was before he succeeded to the title, had left a lumber camp in Upper Canada when the call of the Great War brought Britishers from all the wild places of the world to join the colours. He served as a private in one of the Canadian Regiments, rapidly winning his way upward, and finally being awarded the Victoria Cross for a piece of dare-devil folly--so his comrades declared--that had led to the capture of an important German position and had helped very materially to bring about one of the most brilliant of the many successes scored by the Canadians in the closing stages of the fighting.

That episode seemed to mark the turning-point in the fortunes of James Mitchell. From then onward it seemed as though Fate had no gifts that were too good to be showered upon him. It was only a few weeks later that the obscure Canadian private was summoned to headquarters to receive the astounding intelligence that through a series of deaths that in fiction would have been deemed fantastic, he was a peer of the United Kingdom with a vast fortune at his disposal.

Then James Mitchell, Baron Renstoke, went back to his trenches and the comrades he had learned to love to finish the work on hand.

It was during the latter half of the war that James Mitchell found himself swept by chance into the strange web of mystery and adventure that surrounded the doings of Yvette Pasquet and Dick Manton. He had been detailed, quite privately and "unofficially," to help Yvette in one of her achievements, and the clever French girl had been quick to recognise in him an assistant of more than ordinary ability. Yvette was one of those rare people who never forget, and so there came about a gradual friendship which included Dick Manton and Jules Pasquet. Yvette rejoiced unfeignedly when, after the Armistice, she learned of Mitchell's good fortune. The friendship continued and ripened, and Yvette, Jules, and Dick Manton were staying at Renstoke Castle when a terrible stroke of malign fate cut short a career of brilliant promise and brought an ancient lineage to an end.

Renstoke Castle was a wonderful old house in Argyllshire, and James Mitchell, now Lord Renstoke, was surely one of the favoured of the gods! Over six feet in height, strikingly handsome and of superb physique, wealthy and with great charm of manner, there seemed to be nothing to which he could not aspire. Despite the surroundings of his early years he had been well educated for his father, though only a Canadian farmer, had been a man of considerable culture and learning, and had seen that his son, who inherited his own intellectual gifts, had been well taught. Only the spirit of adventure had led him at twenty-one into the wild places of the world, where he saw existence from many angles, and in a rough outdoor life had brought to perfection physical powers which had been remarkable even in boyhood.

He was now the last of the Renstokes. But he was still young. No one dreamed but that he would marry and that the ancient line would be continued.

Then the blow fell!

Through the late summer a series of mysterious attacks had been made on live stock throughout the western portion of Argyllshire. Sheep, and even deer, had been attacked, evidently by some unusually powerful animal.

Sheep worrying, of course, is not an uncommon vice among dogs, and when the outbreak first started little was thought of the matter. The local farmers and shepherds merely began to watch their dogs more closely than usual. But the outbreaks continued, more and more sheep were killed, and at length the losses became so heavy that drastic steps were taken.

For thirty miles around, not a dog was permitted off the chain after dusk. Bands of men armed with guns, with instructions to shoot any dog on sight, patrolled the country-side by day and night. It was all in vain. Sheep continued to perish under the teeth of the mysterious prowler, and even the smaller deer, in spite of their speed, began to fall victims.

The farmers were at their wits' ends when the mystery was suddenly lifted into the region of unadulterated horror.

Alan MacPherson, a young gamekeeper, had been one of a number of men who, stretched out into a line a couple of miles long, had set out at nightfall to search a lonely piece of moorland in which it was thought the strange animal might be hiding. The line of men had gone forward on a prearranged plan for five or six miles and then "pivoted" on the right hand man, swung round and marched homeward, concentrating finally at a big farm known as Kelsie, where the losses had been very serious.

The men, of course, knew the country thoroughly, and similar manoeuvres had been many times repeated without mishap. Always the last man of the line had turned up within a few minutes of the prearranged time.

On this occasion MacPherson was on the extreme left wheel and, having farthest to go, should have been the last man home. No one was uneasy when it was found he was a few minutes late; he was armed and knew the country like the palm of his hand.

But when the minutes slipped by without news his companions began to be anxious. Three hours passed, and, at length, a search party was hastily formed.

Two hours later MacPherson's body was found lying terribly mangled beside a big rock on the slope of a small tor. His gun, still loaded, was only three feet away. Beside the body lay a filled pipe and a box of matches. Evidently the man had laid down his gun to light his pipe and had been suddenly attacked and killed before he could raise a hand to defend himself.

A few minutes later, Lord Renstoke, Yvette, Dick Manton, and Jules were on the scene. Though all were familiar with the ghastly sights of war, they found themselves in the presence of a horror which overbore all their previous experiences.

Renstoke, whose experience abroad had made him familiar with many wild animals quite unknown to the others, examined the body carefully. At length he rose from his knees with a horrified expression in his eyes, and gave brief orders for the removal of the body to the unfortunate man's home to await the inquest.

But it was not until they had returned to the Castle that he spoke of what he had seen. And his first words gave his comrades a terrible shock.

"No dog did that!" he said quietly, but in a tone of intense conviction.

"Whatever do you mean, Renstoke?" asked Dick quickly. "What else could have done it? There are no lions or tigers about here, you know."

"Are you sure?" replied Renstoke. "I think we shall have to see Erckmann about this." Boris Erckmann, he went on to explain, was a famous zoologist who lived in a big lonely house on the Renstoke estate some ten miles away. He had spent many years in wandering explorations in tropical countries and was known in the inner circles of science as a man of brilliant attainments. He did not advertise himself, however, living the life of a recluse, and to the general public his name meant nothing. Among his Highland neighbours, a dour people who concerned themselves very little with the affairs of other folk, little notice was taken of him. He lived at Lockie, a big house surmounted by a high wall and perched on a gaunt hill-side overlooking a lonely glen. Among his neighbours, who guessed nothing of his wonderful abilities, Erckmann passed for a harmless scientist and was affable and good-natured to those he chanced to meet during his incessant pilgrimages over the wide moorland which stretched for many miles around Lockie.

"Erckmann is said to have a lot of wild animals at Lockie," Renstoke went on to explain, "and it is possible that one of them may have broken loose. I am perfectly certain MacPherson was not killed by a dog."

"But what makes you so certain?" Dick questioned. "So far as I could see any big dog could have done it."

"Did you ever see a dog with hands, Dick?" asked Renstoke quietly.

His hearers started simultaneously with a gasp of horror.

"Whatever do you mean?" they asked.

"Just this," Lord Renstoke replied. "He was not killed by a dog at all. As you saw, the front of his throat was badly torn. But on the back of his neck were two distinct bruises, one on each side and nearly meeting, which suggested the mark of two thumbs, as if he had been seized from behind by two hands which clasped his neck. Now, no dog could have done that. Moreover no dog could have killed him so quickly that he never had a chance either to fight for his life or to call for help. Remember, he was an extremely powerful man and his nearest neighbour in the line was scarcely more than a hundred yards away. He was killed so suddenly and so swiftly that he had no time even to shout. I have seen many men who had been killed by wolves, bears, and cougars, but never one who had not made a fight for his life."

"But what could it have been?" asked Yvette in a horrified whisper.

"There is only one animal in the world that could have done it," replied Renstoke, "and that is a gorilla. You know the strength of the gorilla compared with that of a man is enormous. It has enormously powerful hands and teeth. A man seized unawares, as MacPherson must have been, would be dead in a few seconds; he wouldn't have the smallest chance either to defend himself or to shout. And I happen to know, though it is not generally known, that Erckmann actually has a gorilla at Lockie. I am going over to see him after the inquest and I mean to see the gorilla as well. Erckmann is a tenant of mine, though, as it happens, I have never seen him.

"But there is one thing that puzzles me," Renstoke went on after a pause. "The sheep-killing has been going on for several months, and I don't see where such an animal as a gorilla, assuming that it has been at large for so long, can have been hidden without being seen. But, of course, the country is very wild and there are some big woods that may have screened it during the daytime."

"What are you going to say at the inquest?" Dick asked abruptly.

"Nothing at all until I know a lot more," answered Renstoke deliberately. "Remember, we don't know anything positively yet. I am only giving you my personal opinion."

All agreed that Renstoke's plan was best. But they had yet to learn how far the appalling reality outstripped the horror of their suppositions.

The inquest, held the following afternoon, was almost formal. There was no real evidence, of course, as to how the unfortunate man was killed, and what amounted to an open verdict was found. Neither the doctor who examined the body, nor the detectives from Glasgow who made every possible inquiry, struck the chain of reasoning which had led Renstoke to his strange theory, and it was generally assumed that MacPherson had been killed by some ferocious dog which had been lurking unseen for months in the wild country around Renstoke.

Next morning all four started for Lockie. Erckmann's house, though only ten miles away in a direct line, was at least thirty by road, and as the day was fine they decided to motor for about five miles, leave the car, and walk across country for the remainder of the distance. It was this decision which led them to the first strange clue in the solution of the terrible mystery.

At the point where they left the car, the road, which had been leading westward, made an abrupt turn at the summit of a desolate hill, and stretched away southward as far as they could see. Their destination was further west, and as Dick ran the car on to the grass at the side of the road, they prepared for their tramp.

They had walked some four miles over rough heather-clad country when Renstoke pointed to a big building a mile away and facing the top of the steep rise they had just breasted.

"That is Lockie?" he said.

For the most part, the country was dry. Below them, however, was a shallow valley, along the bottom of which a rippling burn wound its way. Descending the hill they crossed the brook and soon found themselves at a tiny bridge beside the only gateway they could see in the high stone wall, surmounted by a formidable barrier of barbed iron, which surrounded the building.

In response to Renstoke's knock the door was opened by an ill-favoured individual, evidently a foreigner, who stared at them in blank surprise.

"I want to see Mr Erckmann; is he at home?" Renstoke demanded.

The man made some reply in a language which neither of them understood. Renstoke repeated his question.

Turning to a telephone which stood on a small table in the lodge the man spoke a few words. A moment later he signed to them to enter and conducted them to the entrance door of the big house.

As they approached a big, powerfully built man, heavily bearded and wearing round horn spectacles, met them on the steps of the front door.

Renstoke bowed courteously. "Mr Erckmann?" he inquired.

"Yes, I am Mr Erckmann," was the reply. "What can I do for you?"

Renstoke as briefly as possible explained what had happened. Erckmann listened patiently and carefully. Only at the end of the story, when Renstoke told him quite frankly his suspicions, the man's eyes hardened ominously and his lips tightened under his heavy grey moustache.

"Yes, I have a gorilla," he admitted. "But if you suggest that it has escaped you are quite wrong. It has never left its cage since it was brought here, quite young, six years ago. It would be a bad thing for some one if it did," he added.

"May we see it?" asked Renstoke quietly.

"Yes--if you doubt my word," snapped the scientist. He was evidently, for some reason, much annoyed and was controlling himself with obvious difficulty.

During the conversation Dick had once or twice glanced at Yvette and was surprised at the fixity of the gaze she directed at Erckmann. She was regarding him almost as if fascinated, with every sign of horror and apprehension.

Without further words Erckmann led the way through a small paddock to a row of cages, heavily barred with iron, which stood at the rear of the house. Before one of the strongest he halted.

"There you are," he said grimly.

Inside the cage, erect on its hind legs, stood an enormous ape, shackled by a huge chain round its neck to a heavy stake driven into the ground. Nearly seven feet high, it was so horribly repulsive in its perverted likeness to humanity, that Yvette, Dick, and Jules turned away sick with disgust and horror. It snarled and chattered at the sight of the strangers.

Renstoke, however, carefully examined the monster. But he soon realised that this creature had certainly not been at large, at any rate for some considerable time.

The clue had failed. Whatever the truth might be it was clear the gorilla could have had no part in the terrible tragedy of Alan MacPherson.

"A wonderful specimen," said Renstoke, turning to Erckmann. "Have you had him long?"

"About six years," the scientist replied. "Would you like to see what it can do?" Without waiting for a reply, he spoke softly to the raging beast in some language the others did not understand.

Instantly the brute calmed down, shuffled to the bars of the cage and laid its head on the ground close to where Erckmann was standing. It was just as though a dog were fawning on its master. Erckmann fearlessly thrust a hand between the bars and scratched the repulsive head while the great ape lay with closed eyes evidently in keen enjoyment of the sensation.

Still talking quietly in the strange language, Erckmann put the beast through a number of tricks which it performed, clumsily, of course, but with obvious understanding of what was required of it. It was, as Renstoke realised, a wonderful example of animal training, for the gorilla is perhaps the most intractable of all living animals.

"Perhaps as you are here you would like to see the rest of my menagerie," said Erckmann, as he led the way to a series of cages adjoining.

They gazed in astonishment at what they saw. There was a superb tiger, several leopards of different species, and at least a dozen wolves. The animals were all clean and well cared for and it was obvious at a glance that none of them could have been wandering for an indefinite period about the country.

"I hope you are satisfied, Lord Renstoke," said Erckmann at last, "that none of my pets is responsible for what has happened?"

"Quite," replied Renstoke. "And I am sorry we had to trouble you. But I am sure you will understand why I came. The affair is so mysterious that I could not leave any possibility unexplored." Erckmann had puzzled them all. The man was perfectly courteous and apparently quite open in his replies to their questions. None the less all sensed that he was ill at ease and that he quite certainly resented their intrusion.

Yvette, more sensitive and keenly strung than the others, shuddered violently as they left the house.

"That man is bad, all bad," she declared vehemently. "He has the eyes of the snake." She had put into words what all had felt, yet had been half ashamed to confess. There was something repulsively snake-like in the steady glare of Erckmann's eyes behind the thick round glasses.

"I confess I feel like Yvette," said Dick, "the man gave me the creeps."

Renstoke looked grave.

"He didn't strike me as being quite aboveboard," he admitted. "At the same time, I don't see what he has to conceal. All the cages were occupied and it is certain none of the animals had been loose recently, and if one had broken out there is no reason why he should not say so. But he may have another ape which he has not shown us?"

They walked a few hundred yards in silence until they had got to the bottom of the hill and approached the little burn that ran down the valley. There was no path, and as chance would have it, they deviated a few yards from the way along which they had come. They were crossing the brook when Yvette gave a slight exclamation.

"Oh, look here," she said.

The bed of the burn was stony throughout, but at one point, at the very edge of the water was a tiny patch of sand, smooth and firm and hardly larger than a handkerchief. Yvette pointed to it.

There, sharply and clearly defined, was the unmistakable imprint of a naked, misshapen foot! It was human beyond all question. It pointed in the direction of the house they had just left, and it was dear that the barefooted walker, whoever he may have been, had stepped from the heather just on to the patch of firm sand and been carried by his next stride through and beyond the rivulet on to the heather and stones where no footprints would remain. By some strange chance that one tell-tale footprint had been left in perhaps the only square foot of ground for miles where an impression could be left!

They examined the footprint with eager curiosity. Evidently the walker, or rather runner, had come fast down the hill, for the front part of the foot was driven deeply into the sand while the heel was only just showing.

"He must have been running," said Renstoke, "and what kind of man could run over such a country as this?"

The question was natural, for the heather grew thick and deep round there and they had found walking difficult enough; running would have been out of the question for any of them.

They were puzzled by the strange footprint, but how little they guessed that it held the key to the terrible tragedy of Renstoke!

Late that night, Renstoke, Dick, and Jules sat yarning in the great old drawing-room at the Castle. The night was close and sultry, with a threat of thunder in the air, and the big French windows which opened on to the spreading lawn were flung wide.

They were discussing Erckmann.

"I didn't like him," said Renstoke, "though it is recognised that he possesses genius in a marked degree."

"Oh! You've heard something then?" asked Dick quickly.

"Yes. The general public know nothing of him, but I hear that he has an amazing theory that it is possible, by an operation on the brain, to abolish almost entirely the ordinary characteristics of a man or an animal, and by the injection of an appropriate serum to substitute the mental, and to some extent the physical, characteristics of another species. He believes that you can, for instance, take a puppy-dog, operate on its brain, inject a serum prepared in some way from the brain of a monkey, and the puppy will grow up with the mentality and habits of a monkey and with its bodily characteristics so transformed that it can do many things--such, for instance, as climb a tree--which no dog could do. I believe he has actually succeeded in doing this!"

"How weird and extraordinary!" remarked Yvette.

"More than this, he believes you could do the same with a human being-- destroy its human attributes and give it, for example, the ferocity, and something of the speed, of a wolf or a tiger."

"How on earth did you learn this, Renstoke?" asked Dick.

"From perhaps the only person who ever knew Erckmann really well," was the reply. "Some years ago Erckmann was the resident doctor at a lunatic asylum in Prague. He made a particular crony of his chief assistant, a young doctor named Chatry, who afterwards went to Canada, where I met him. Chatry told me something of Erckmann's views and experiments. I was, of course, tremendously interested, but I little thought I should ever run against the man in the flesh. Erckmann was undoubtedly a very able man, but there was a scandal. On some pretext or other he performed a remarkable operation on an insane person. The patient, who had previously been quite tractable, developed extraordinary characteristics. He growled and snapped at all who approached him, insisted on eating his food on the floor instead of at table, barked like a dog, and finally would only sleep curled up on a rug. In fact, he developed strikingly dog-like habits. How much of anything Erckmann let out generally Chatry never knew. But he was asked to resign, and he left Prague."

"A very curious story!" Dick remarked.

"Now Chatry had no doubt whatever on the subject," said his host. "Amazing as it may seem, he was firmly convinced that Erckmann had deliberately made this extraordinary experiment and that it had succeeded. Chatry died just before I left Canada, but before he died, he gave me a little manuscript book in which he has related the whole story. I'll show it to you to-morrow."

They said good-night and went to bed, leaving Renstoke, who sometimes suffered from insomnia, to read himself sleepy.

It was about two o'clock when Dick, who was a light sleeper, was roused by a shout for help, apparently from the drawing-room which was directly below his bedroom. Instantly he sprang out of bed, and snatching up a revolver, rushed downstairs.

But he was just too late.

As he entered the brilliantly lighted drawing-room he caught sight through the open window of a heavy misshapen body disappearing into the gloom beyond the bright patch of light cast by the electric lamps on the lawn outside.

Renstoke lay on his back on the floor, dying beside his favourite chair. Close by was the book he had been reading and on the carpet near it was his pipe, the tobacco still smouldering.

Dick knelt hastily by the side of his friend and sought frantically to revive him. But it was in vain. The young peer died in his arms. It was evident that he had been attacked without the slightest warning, and mercilessly strangled.

And in the side of his throat, just above the jugular vein, was a deep wound, horribly lacerated, from which the blood flowed in a heavy stream.

The Castle was speedily aroused, and in a few minutes half a dozen men were busily searching the surrounding country. But it was in vain--the mysterious assailant of the unfortunate Lord Renstoke had vanished completely.

The following day Dick, Jules, and Yvette, almost overcome with grief, were discussing the loss of their friend.

"There is some devilry at work," Dick declared. "And I shall never rest till it is cleared up, if I spend the rest of my life here."

Yvette burst into a furious philippic against Erckmann. "That man is at the bottom of it all," she insisted.

"But, Yvette," Dick remonstrated, "we have no kind of evidence of that."

"I don't care," she replied vehemently, "Erckmann knows all about it. I should like to choke it out of him," she ended viciously in French.

"Well," said Jules, "we can't go to Lockie and accuse him. How about trying a trap of some kind?"

"We might do it in that way," Dick admitted. "But what kind of trap?"

Long and eagerly they discussed the matter, and at length a plan was evolved.

The next morning brought them a visit from Inspector Buckman, one of the ablest men of the Special Branch at Scotland Yard, to whom, utterly baffled, the police had very wisely applied for help. He was well known to all of them as a keen, capable man of infinite resource and undaunted courage.

Buckman listened closely while Dick ran over the story, putting in a keen question here and there.

"We have got to keep the real facts quiet," he said at length. "Erckmann must not suspect that we have the smallest inkling of the evidence of Lord Renstoke's death. I will fix that up with the coroner."

It was an easy matter. Renstoke Castle was a remote spot, and while the affair, of course, could not be entirely concealed, it was a simple matter to keep the exact details secret. All the public learned was that Lord Renstoke had been attacked and murdered presumably by a burglar for whom a close search was being made.

But behind all and working in secret the keen brains of Dick, Yvette, Jules, and Buckman were busy.

Two or three nights later the word went round to the scattered farms that every single head of stock was to be driven in to the farms and rigidly confined in the buildings from dusk to daybreak. So far as they could ensure it not a single living thing was at large.

Dick's trap was arranged on the hill-side a mile from Renstoke.

Four inches above the ground, in a circle fifty yards in diameter, ran a thin electric wire supported at intervals on small insulated posts. Just inside the circle, on the side away from Renstoke, a sheep was tethered to a strong stake. In the centre of the circle from a tall pole hung a powerful magnesium flash, electrically connected so that it would be at once exploded by any pressure on the encircling wire, and momentarily light up with day-time brilliance a large patch of the surrounding country.

As dusk fell, Dick, Yvette, Jules, and Buckman carefully crossed the wire and took up their positions in the centre of the circle, lying full length in the sheltering heather, and each with a revolver ready to hand. In a leash beside Dick lay Spot, his favourite Airedale, who could be trusted to give warning of the approach of any intruder, and afterwards to track him remorselessly.

As the leaden moments dragged by it grew darker and darker until the country-side was plunged in pitch blackness. The strain on the watchers was terrific. They could not smoke or talk, they hardly dared to move.

Hour after hour dragged by. Midnight passed. Dick, half asleep, was gently stroking the back of the Airedale.

Suddenly he felt the animal stiffen, and the hair along its back bristled ominously. A moment later the dog gave a low, half-audible growl and rose to its feet. Instantly the party were keenly alert.

Dick clapped his hand over the dog's muzzle, and the well-trained animal subsided into silence. But Dick could feel that it was strainingly alert; obviously it sensed an intruder.

Keenly at attention, with every faculty strained to the utmost, the silent watchers heard not a sound. But a few moments later there was a vicious snap in the air above them as the magnesium flash exploded, turning the inky blackness for a fraction of a second into a blaze of dazzling light.

In that brief outburst of radiance the four caught a glimpse of a horror that photographed itself indelibly on their memories.

Twenty-five yards away a bestial, hideous face loomed out in the glare of light. It was the epitome of all things evil, with wild matted hair, staring eyes and a horrible misshapen mouth drawn back in a snarl which showed two rows of monstrous teeth. The body they could not see. Apparently the creature was crouching in the heather so that only its ghastly head was visible.

Had it been a wild animal not one of the four, their nerves steel-hardened by the war, would have felt a tremor. But that ghastly face, vile and brutal as it was, was unmistakably human, and for an instant the watchers were paralysed with uncontrollable terror.

But it was only for a moment.

Four revolver shots rang out almost simultaneously, fired in the darkness at the spot where the apparition had appeared. A crackling volley followed as the four automatics were emptied. Almost with the last shot came a howl of mingled rage and pain from the darkness. Evidently a bullet had got home.

A few moments later Dick, with Spot barking madly and tugging wildly at his leash, had plunged into the blackness in hot pursuit at the fiendish intruder. Close behind him came Yvette, Jules, and Buckman.

The hunt had begun!

Of that wild dash across country in the darkness Dick afterwards remembered but little. Spot plunged ahead without hesitation and Dick followed, intent only on making the best speed possible and careless of constant falls as he stumbled blindly along. He dared not loose the dog, for without it he would have been helpless, and he plunged blindly forward, his reloaded pistol grasped in his right hand, careless of himself and intent only on overtaking the horror which he knew lay somewhere ahead of him. Behind him toiled the others, guided by Spot's frantic barks.

Progress, of course, was slow; falls and stumbles every few moments checked the pace; the darkness was baffling. It was with feelings of intense relief that Dick at length saw the silvery edge of the moon lifting itself above the hills behind him. He had lost all sense of direction, but the moon rising behind him told him he was travelling westward.

Half an hour later the country was bathed in soft light and Dick was able to pick up his bearings. Suddenly he realised with a shock that he was heading straight for Lockie!

Dick halted to let the others come up. Without being afraid he felt instinctively that something terrible lay ahead of them and that for safety's sake it were best that they should be together.

They were a sorry-looking party--hatless, their clothes torn, their faces and hands bruised and scratched by constant falls, almost exhausted by their tremendous efforts. But none of them thought of giving up the chase.

For another mile they pushed onward, making better progress in the growing moonlight.

Suddenly Buckman gave a tremendous shout. "Look there!" he roared, pointing to a low hill which ran across their path.

Not five hundred yards away, on the top of the rise and clearly silhouetted against the sky, they caught a glimpse of a monstrous figure which, even as they looked, vanished over the crest and was gone. It was, unmistakably, a man of giant stature! It moved stiffly as though in pain; evidently one of the shots fired in the trap had got home.

They hurried on. When they reached the crest of the rise Lockie lay before them, and they could see the monstrous figure crossing a tiny stream in the valley below.

They were gaining rapidly now. Dawn was breaking and the cold pale light allowed them a dear view.

The creature ahead of them was toiling painfully up the slope which led to Lockie. Suddenly a man issued from the house. It was Erckmann and in his hand he carried a formidable whip.

Less than two hundred yards away Dick and his companions halted spellbound. In some mysterious fashion they realised that they were to witness the last act in the terrible drama.

The end came swiftly. More and more slowly, almost crawling at last, the strange creature approached Erckmann and at length, evidently utterly exhausted, collapsed at his feet in a heap.

They heard the scientist shout something unintelligible. Then he raised his heavy whip and struck with fearful force at the unfortunate thing which lay before him.

It was a fatal mistake. With the speed of lightning the misshapen heap on the ground flashed into furious activity. All the horrified spectators saw was an instantaneous leap and a brief struggle, and Erckmann and the Thing locked in a deadly grapple and then drop motionless.

Dick covered the last hundred yards in a furious dash. But he was too late. Erckmann lay dead, with his adversary dead on top of him. The zoologist had been killed almost instantly by the grip of two large hands that still encircled his neck in a vice-like clutch, and in his throat the misshapen fangs of the creature were still buried deeply. Only with infinite trouble was the body of the scientist freed from that deadly grapple, and they were able to examine the monster that had spread terror and death through Argyllshire.

Unmistakably the body was that of a man, but incredibly dehumanised and ape-like. The muscular development was tremendous; the hands and arms were knotted masses of titanic muscle. But the crowning horror was the face--low-browed, flat-nosed, with a tremendous jaw and long pointed teeth, utterly unlike anything human. The body, stark naked, was covered thickly with hair and in the side was a terrible wound evidently made by the impact of a soft-nosed bullet from one of the automatic pistols. No normal human being could have survived it for more than a few minutes.

It was only later, when they searched Lockie, that they realised fully that Erckmann had fallen a victim to a monster he had himself created. His diaries proved that Chatry had spoken the truth. They were a repellent but horribly fascinating account of his experiments. Of the results he had written in a wealth of detail, but of the process he employed there was not even a hint. That awful secret he had kept to himself, and had taken with him to his grave.

They found that he had, as Chatry had said, taken a human being, obviously of low mental development--possibly an asylum patient--and practically, by some devilish discovery, converted it into a human ape, endowed with the blood-lust of the tiger. But whether the fearful creature was capable of receiving and acting upon instructions, or whether Erckmann simply let it loose to follow its terrible instincts until the "homing" instinct brought it back they never learned.

Of Lockie, the police decided to make a clean sweep. The animals were shot and the half-dozen evil-looking foreign servants were paid off and sent to their homes, mostly in the wilder parts of Transylvania. They one and all refused to say a word. Whatever they were, they were at least faithful to their dead master.

Then, in the magnificent chemical laboratory with which the house was equipped, Dick, who found himself Renstoke's sole executor, easily arranged an "accident." Fire broke out, there was no help for miles around and in a couple of hours the ill-omened house was a heap of ashes. The Spectre of Lockie had been finally laid.

CHAPTER SEVEN.

THE PERIL OF THE PREFET.

It was a mystery of the City of Paris which engaged the trio--a secret that has never been told, though many enterprising newspapers have tried to fathom it. Here it is related for the first time.

On a gloomy mid-December morning the sensation-loving Parisians awoke to a new and eminently agreeable thrill. It was only last year and the occasion will be well remembered.

There had been trouble enough in the City of Light, which for once at any rate belied its name. A series of strikes had half-paralysed the capital. Coal and light were almost unobtainable; the public lamps remained unlit; at night the City of Pleasure was plunged in profound gloom. There were misery and wretchedness in the haunts of squalor and poverty which flanked the wealthier districts where, at a price, all things agreeable were as usual obtainable.

But the dumb underworld was becoming vocal!

"A Mort L'Assassin!" At daybreak the startling legend suddenly, and without warning, revealed itself from a thousand vantage-points to the awakening city. In crude, blazing red it flared from the hoardings-- sinister, ill-omened and, above all, full of significance. Parisians alone knew.

There could be no possibility of doubt as to the individual referred to. It was, beyond question, Raoul Gregoire, the Prefect of Police, whose cold, ruthless vendetta against the dark, turbulent forces which flowed beneath the effervescent gaiety of the gay life of Paris, had earned for him the vindictive hatred of the criminal world, and had gained him his unenviable sobriquet of "Assassin!"

For months Raoul Gregoire's life had hung by a thread. Before his appointment he had been Prefect of Finisterre. A series of efforts to "remove" him had been defeated only in the nick of time. Twice he had been badly wounded. Once a bomb had wrecked his car just after he had left it. A less courageous man would have given up the unequal contest and sought a pretext for retirement--back to the quiet, sea-beaten coast of Finisterre.

But Monsieur le Prefet was of a different mould. Stern and ruthless he was, but his courage was invincible. He remained calm and imperturbed-- far more so, indeed, than many of his subordinates, who feared that the vengeance of the underworld might fall, by accident or design, upon themselves.

"Gregoire has pushed things a bit too far," was Yvette's verdict, as she talked over with Dick Manton and Jules the latest and most blatant challenge to the forces of the law and order. "They mean to make certain this time. I'm sure of it?"

"It certainly seems so," Dick agreed. "But I wonder when and how it will be? That's the point. Gregoire doesn't show himself much in public now; he is practically living in the Prefecture, and surrounded by his agents he is far too well guarded for any attempt to be made there."

"They will have a good chance at the Sultan's reception," remarked Jules reflectively. "Monsieur le Prefet will have to be in the procession--he can hardly stay away even if he wanted to. It would show the white feather."

It was a day to which the gaiety-loving Parisians were looking forward with special interest. France's age-long quarrel with the wild tribes of the Morocco hinterland had at length been amicably settled, and their Sultan, Ahmed Mohassib, a picturesque figure whose eccentric doings provided the gossip-loving boulevard with hundreds of good stories, was "doing" Paris as the guest of the Quai d'Orsay. It was expedient to show the barbaric ruler all the honour possible, and the following Friday was the day on which he was to pay a ceremonial visit to the Elysee. There was to be a great procession, and the Government had let the Press understand that a skilfully worked-up popular demonstration was desirable. The papers had responded nobly, and it was certain that "tout Paris" would be out to see the show.

On the occasion, at any rate, Monsieur le Prefet must be greatly in evidence. He was responsible for public order and must ride in the procession whatever the risk to himself, a plain target, for once, for the bullet or bomb of the assassin.

"To-day is Saturday," Yvette remarked. "We really have not much time to spare between now and the twenty-second. I think I will make a few inquiries to-night. Jules had better go with me."

Dick's heart sank. He knew what Yvette's "inquiries" meant--hours, perhaps days, spent in the lowest quarters of Paris, surrounded by such horrible riff-raff that if her purpose were even suspected her life would be worth hardly a moment's purchase.

But he knew it was useless to remonstrate. Yvette had a perfect genius for "make-up," and what was far more important, a perfect knowledge of the strange _argot_ which served the underworld of Paris. Jules was almost as clever as Yvette. But in this particular, of course, Dick was far behind. He could not hope to sustain his part in surroundings where a single wrong word would mean instant suspicion, and probably a swift and violent death for all three.

"I wish I could go with you, Yvette," he said wistfully, "but, alas! I know it is quite impossible."

Yvette had many friends in the lower quarters of the Montmartre. The proprietors of many of the low _buvettes_ of the slums--places where one could get absinthe and drugs--were secretly in her pay, and so far as they were concerned she had no fears; the traffickers trusted her because they knew their secrets were safe. And by an ingenious code system which depended upon a mere vocal inflexion of certain common words she could reveal her identity, no matter what her disguise, to those who were in her secret.

Darkness had fallen upon the city when two appalling specimens of the worst vagabondage of Paris--a man and a woman--crept silently through the market quarter towards one of Paris's vilest haunts of villainy. They were such woebegone specimens of humanity as might have served for figures in some new "Inferno." Bedraggled and unkempt, their hands and faces besmirched with grime, their clothes hanging in tatters, it would have been impossible for even the keenest eye to have detected the smart French girl and her usually debonair brother. So far as appearances went they were safe enough. The risk would come when they began to talk, and especially when they began to ask questions. Here a slip of the tongue might betray them. But the risk had to be taken.

The Prefet himself, quite as anxious as Dick for the safety of Yvette and Jules, had taken precautions to protect them as far as possible. Actual escort, of course, was out of the question. Both Yvette and Jules carried revolvers, but in addition Jules had concealed in the ample pockets of his villainous clothing, a tiny but delicate wireless telegraph apparatus, powerful enough upon a dry battery to send out a wireless wave which would carry a thousand yards or so.

This dainty little bit of electrical work was the invention of Dick Manton. Hardly larger than an old-fashioned watch it was operated by a hundred-volt battery which fitted into a specially made pocket, and the tiny transmitting key could be operated with one finger without arousing the slightest suspicion. Gregoire's agents were dotted thickly around the unsavoury neighbourhood, each in touch, by means of the wireless, with every movement Yvette and Jules might make. Dick himself was not far away. How amply these precautions were justified the events of the night were to show.

For hour after hour Yvette and Jules slunk from one haunt of vice to another, always keenly on the alert, frequently helped by one or another of Yvette's disreputable friends, but yet unable to pick up the slightest vestige of the trail of which they were in such active search.

At length their patient vigil culminated.

Plunging deeper and deeper into the labyrinth of the slums, they had penetrated at length to a tiny bar in the very lowest and most dangerous portion of the market section. The place was crowded with a mass of riff-raff at which even Yvette and Jules, accustomed as they were to such sights and sounds, could not repress a shudder.

The proprietor, as it happened, was a beetle-browed Provencal whose one redeeming feature was gratitude to Yvette. His character was utterly bad and he had been mixed up in dozens of affairs more or less disreputable. A year or two before a serious charge of which he happened to be innocent had been brought against him. Yvette had managed, with considerable trouble, to lay the real culprit by the heels, and Jules Charetier, Apache though he was, would now go through fire and water to serve her. Yvette knew that in his house she was personally far safer than she would have been in many more pretentious establishments.

Charetier raised his eyebrows when he caught the slight inflexion that instantly revealed to him Yvette's identity. But he took no further notice beyond serving the drinks for which she had asked.

A moment later, with a significant look, he quitted the room. Yvette, with a slang caution to look after her drink for a moment, slipped into the filthy street and round the corner to the side entrance of the house. Charetier was waiting for her, and a few moments later they were seated in the man's dingy room on the floor above the bar.

"Whatever are you doing here, mademoiselle?" Jules burst out impulsively. "This is no place, even for you!"

"Listen, Charetier," replied the girl rapidly. "Something is brewing for next Friday. Something serious! You have seen the posters. I _must_ find out about it. Can you tell me where any of the `Seven' are to-night?"

Jules Charetier paled at the mention of "The Seven," the powerful camarilla whose hidden influence was felt throughout the criminal underworld of Paris, London, and New York. The men who, practically without risk to themselves, were responsible for half the anarchist crimes of the three great capitals. Who they were, and their real names, not even Yvette knew. Never appearing directly themselves, they worked entirely through agents, and fighting against them, the police found themselves in a stifling fog of mystery. But, as Yvette knew, Charetier was deep in the councils of Continental Anarchism, and she knew, too, that in his hands the life of the ordinary police agent would have been worth nothing. Even for herself she was not very confident, but she had decided on a bold stroke, trusting Charetier with everything on the ground of the service she had done him.

At first the man was obdurate.

"Not even for you, my dear mademoiselle," he said sullenly. "But, mademoiselle," he went on earnestly, "we have been friends, therefore I implore you for your own sake to drop the matter and get away as speedily as possible. I cannot tell you anything."

Yvette's revolver flashed out and in an instant she had the innkeeper covered.

"Listen, Jules!" she cried imperiously. "My brother is below, and the house is surrounded. If I stamp upon the floor you will be raided instantly. And you know there are things here you would not like the police to see--they don't know it, but you and I do! Suppose Demidoff learned that his papers had fallen into Raoul Gregoire's hands--eh?"

For a moment Yvette thought Charetier would have risked everything and sprung at her. But it was only for a moment. Then he collapsed. It was evident he feared Demidoff, the notorious Bolshevik agent, even more than he feared the police.

"Very well, mademoiselle," he replied, beads of perspiration standing out upon his wide white forehead and, despite his bravado, a hunted look crept into his eyes. "You might try the `Chat Mort.' There will be a meeting there at three o'clock this morning. But again I implore you not to go. You cannot get in and if you did you would never come out alive."

"In which room do they meet?" was Yvette's only reply.

"The one at the back, looking out upon the old courtyard," was Charetier's reply. "I know no more than that."

"Thanks, Charetier," said Yvette as she rose to go.

"But, my dear mademoiselle," implored the innkeeper, "you will not breathe--"

Yvette cut him short.

"That's enough, Charetier," she said in a freezing tone. "You surely know you are safe so far as I am concerned. You have done me a great service to-night and I shall not forget." Five minutes later Yvette and Jules were hastening to the "Chat Mort," a tavern of a gayer night-life than the one they had just quitted. It stood on the corner of two filthy slums in the Villette Quarter and at the rear was one of those tiny courtyards which so often go with old French houses--a place given over to the storage of odds and ends of flotsam and jetsam which are hardly worth the trouble of keeping, or even stealing. Only a rickety wooden fence divided it from the horrible alley deep in mud and refuse.

They realised at once that to enter the house would be impossible. It was now long past two o'clock and the street was deserted; everything was silent as the grave, and from the closely shuttered "Chat Mort" there was not a glimmer of light. To all appearances the inhabitants were soundly asleep.

But Yvette placed implicit trust in Charetier. She was sure that the mysterious meeting would be held at the appointed hour.

They crept silently to the rear of the building, cautiously forced a way through the crazy fence, and a moment later were outside the window of the room which Charetier had indicated as the meeting-place.

Crouching beneath the window they listened intently. They were safe enough except for some unforeseeable accident.

There was no sound in the room; no glimmer of light through the shutters.

Jules took from his pocket a tiny drill which speedily and silently bit a half-inch hole through the rotting woodwork of the window. Into this he thrust a plug which at the end bore an extremely delicate microphone receiver. With telephones at their ears they listened intently. Not a word would be uttered in the room without their knowledge. They could see nothing, but if anything was whispered they would certainly hear it.

The minutes dragged slowly past until just before three o'clock a slight sound caught Jules' attention. Some one had entered the room. A moment later came the rasp of a match being struck.

Three o'clock boomed from a distant church dock. Footsteps echoed inside. The meeting was assembling!

How they longed to see into that room of mystery! But that was impossible; they must rely upon the microphone alone for all the information they could obtain. Jules' hand sought Yvette's wrist, and in the Morse code he tapped out with his fingers--he dared not speak--a caution to listen acutely. Their only hope of identifying the criminals was by their voices.

They could see nothing. They could not even tell how many people there were in the room. But the mutter of conversation in varying tones came dearly to their ears. It consisted mainly, as they expected, of fierce denunciation of Monsieur le Prefet of Police, whom they named "the Assassin."

Soon it became clear that the meeting had been called solely to settle the time and place of the attack; evidently the method had been decided upon earlier. Not a single word could the listeners catch of how the attack was to be carried out, whether by bomb, or bullet, or knife. Little did they guess the secret and deadly swiftness of the anarchists' plan.

For some time the discussion continued. Place after place was suggested and rejected upon one ground or another.

Suddenly a hard masterful voice cut across the talking.

"The Place d'Italie will be the best," it declared. "Half the road is up there and the procession must go along the Avenue des Gobelins, close to the old villa. At that distance it will be impossible to miss. And there will be no noise and no fuss till the job is done."

The Old Villa! Jules knew the place well--an ancient building dating back to Louis XV, solidly built, and with all the quaint architectural features of the time. Quite unsuitable for any modern purposes, its vast apartments had by degrees been turned into a queer medley of rooms which served partly as flats and partly as offices to a heterogeneous mass of tenants, many of them of more than doubtful reputation. But how any attack on Raoul Gregoire could be projected from a building which it was certain would, on the day of the procession, be packed with sightseers, Jules was at a loss to conceive.

That, however, remained to be discovered. For the moment the important thing was to capture the band of conspirators before they could make their escape.

Jules withdrew, and adjusting his portable instrument--a marvel of compactness--placed his foot against an iron lamp-post to make an earth contact, and swiftly called the Prefecture of Police by Morse.

The telephones were on his ears, and almost next second he heard the answering signal. Then he tapped out on his wireless transmitter an urgent message. A moment later he and Yvette had slipped clear of the place, and ran swiftly away. It was no part of their plan to risk recognition by any of the prisoners.

At the head of the alley they waited for about six or seven minutes, when they met Roquet, the inspector of the Surete, who was in charge of the detectives who were rapidly converging on the inn. To him Jules briefly explained the situation.

"We have them safely enough," declared Roquet with a strong accent of the Midi. "Every approach has been guarded for the last hour, and no one has been allowed to pass in or out. You can now leave it to us, m'sieur."

Yvette and Jules were glad enough to say _au revoir_ and to hurry home for a much-needed rest. They could examine the prisoners at their leisure at the Prefecture and, if possible, identify them by their voices.

But a startling surprise awaited the detectives.

Their imperious knocking at the door of the frowsy Chat Mort at first brought no reply. A few minutes later the proprietor appeared, half-dressed and yawning drowsily as though just awakened from profound sleep. He was instantly arrested and handcuffed and the police poured into the house, revolvers drawn and ready for what they expected would be a furious combat with reckless and desperate men.

To their utter amazement the house was empty!

The room looking on to the courtyard, in which, according to Jules and Yvette, the conspirators had held their meeting, was in perfect order, apparently as it had been left the night before when the place was shut up. There was not a sign that anyone had been there for hours, not even a whiff of fresh tobacco smoke to suggest that the room had been recently occupied.

Roquet was utterly mystified. He had, with very good reason, dreamed any escape impossible. Could Jules and Yvette have been mistaken?

That, he felt, was out of the question. None the less the problem remained--where were the men? The house was speedily searched from attic to cellars, but in vain. There was not the smallest indication that any meeting had been held there!

Roquet naturally felt intensely foolish, and his embarrassment was in no way lessened by the voluble protestations of the proprietor who demanded, with every show of righteous indignation, the reason of what he was pleased to term "an outrageous domiciliary visit." There was, of course, no charge against him, and ultimately the baffled police were compelled to release him and retire, furious and puzzled at the utter failure of what had promised to be a brilliant _coup_.

Three days later the mystery was solved.

From the cellar of the "Chat Mort" a narrow tunnel had been driven to an equally disreputable establishment a short distance away, and when the police had raided the house the plotters had swiftly bolted, leaving the innkeeper to drop behind them the stone slab in the cellar floor which covered the entrance to the tunnel.

The position now was grave enough, and Yvette, Jules, and Dick discussed it at length with the Prefet and his lieutenants. To all entreaties that he should stay out of the procession the Chief resolutely turned a deaf ear, and they found it impossible to shake his resolve.

Would the conspirators stick to the arrangement made at the "Chat Mort," or would they, alarmed by the raid on the house, make an eleventh-hour change in their plans? That was the problem to be solved.

Monsieur le Prefet was living on the edge of a volcano, and all his precautions would, he feared, be of no avail against them.

Dick felt convinced they would carry out the plan arranged. It could not be imagined, he argued, that they would dream they had been overheard, and it was evident that the plan had been very carefully considered. Ultimately it was decided to relax none of the ordinary precautions, but to keep a specially close watch on the old villa in the Place d'Italie. Dick decided that, whatever the police did, he would make his own arrangements for that purpose. The sequel proved that it was well he did so.

On the night prior to the procession the police carried out a very drastic _coup_. Every known anarchist in Paris was arrested on some pretext or another and locked up. One by one they were briefly interrogated, while Jules and Yvette, concealed in the room behind a screen, tried to recognise any of the voices they had heard in the Chat Mort.

Fifty or sixty prisoners had been interviewed before Jules and his sister standing behind a screen heard a voice they recognised. It was that of the man who had suggested the old villa in the Place d'Italie as a suitable base for the attempt on the Prefet. None of the others could be identified, and it was evident that the worst of the miscreants were still at large.

The man whom they recognised proved to be Anton Kapok, a Hungarian of whom nothing was known except that he was in the habit of delivering violent harangues at Socialist and Anarchist meetings. But it was evident now that he was far more dangerous than the police had hitherto supposed.

Closely interrogated, he denied everything. He knew nothing, he declared, of the "Chat Mort" and had not been mixed up in any conspiracy. His Anarchist proclivities, however, he boldly admitted and declared that the police knew all there was to know about him.

To the police a search of Kapok's room in Bellville revealed nothing more incriminating than a mass of Anarchist literature. But Dick made a discovery which they had overlooked.

Close to the ceiling, immediately above the fireplace, was suspended on two hooks what looked like a rod from which pictures might be hung. The police had, in fact, so regarded it. Dick never knew what aroused his suspicions, but something impelled him to mount a ladder and fetch the rod down. Then he made a startling discovery.

The supposed rod was nothing less than one of the wonderful blow-pipes used by some of the aboriginal tribes of South America and elsewhere to shoot their poisoned darts with which they either fought their enemies or killed dangerous animals. One of the darts, a tiny affair fashioned out of a sharp thorn with a tuft of cotton which just filled the tube, was actually in position.

Instantly Dick's mind travelled back to the strange deaths nearly a year before of two police officials who had been specially astute in the anti-anarchist campaign. Both had been found dead in lonely streets, and in each case the only mark on the body was a tiny scratch on the cheek which no one had dreamed of connecting with their inexplicable death. As Dick gazed at the deadly blow-pipe those scratches assumed a new and sinister significance.

Carefully removing the dart, Dick hurried with it to the laboratory of Doctor Lepine, the well-known toxicologist.

Doctor Lepine smiled.

"Lucky you didn't scratch yourself with it, Monsieur Manton," he said in French. "It would mean almost instant death!"

He listened gravely as Dick described the death of the two police agents. The doctor had been away in England at the time and had not even heard of the circumstances. But he hurried round to the Prefecture with Dick and carefully examined the documents which dealt with the two cases and described minutely the appearance of the bodies.

"I have not the slightest doubt," he declared, "that both men were killed with one of these darts. Every indication points to it. But as the darts were not found we must presume they were removed after death to avoid arousing suspicion. The victim would be paralysed almost instantly, and would fall and die almost on the spot where he was standing when the dart infected him. If there are any more of these accursed things in Paris it will, I fear, be a difficult matter to protect Monsieur le Prefet, for a favourable opportunity must come in the long run."

Dick hurried back to Kapok's room, meaning to secure the blow-pipe. To his amazement the deadly weapon had disappeared! The police agents on duty outside the room asserted that no one had entered. But an open window told its tale; some one had crept along the ledge outside, entered the room and possessed himself of the weapon.

Dick spent several anxious hours with the Prefet, Raoul Gregoire, and Inspector Roquet, arranging a plan of campaign.

Next morning found him crouched in an upper window of a locked room in a house facing the old villa in the Place d'Italie. Close at hand lay a powerful pneumatic gun, a weapon perfected by Jules and almost as deadly and efficient as a rifle. He was haunted by a sickening _sense_ of foreboding. Against every evidence of his reason and senses he felt convinced that it was from that old villa that danger threatened Gregoire.

Yet he was bound to admit that his fears seemed absurd. The old house opposite was packed with sightseers, but there was a detective in every room close to the window. Even the garrets had been searched. It was obvious that they had not been entered for months.

Yet Dick could not shake off the uncanny feeling which haunted him.

At last the head of the procession came in sight, with the blare of military bands and a crash of cheers from the thousands of spectators lining the streets. But Dick had no eyes for the show. His whole attention was riveted on the building before him.

The Sultan Ahmed Mohassib, of Morocco, in his white _burnous_ with many decorations, passed amid a hurricane of cheers. Glancing along the procession Dick saw the Prefet--a soldierly figure sitting erect in his car. In a few moments he would be abreast of the villa.

Suddenly Dick's eye was caught by a flash of light. Glancing quickly upward he saw to his amazement that the window of a garret facing him--a room which had already been searched--had suddenly opened. Only the chance reflection of the sun upon the glass had attracted his attention to the swift movement.

As Raoul Gregoire passed, a dark rod, clutched in a hand which rested on the grimy windowsill, projected itself from the window. It wavered for a moment, then steadied itself and pointed downward.

Instantly Dick fired.

The hand disappeared with a jerk, while the rod slid forward and fell over to the ground!

Wild with excitement Dick dashed down into the street. It was utterly impossible to force his way through the cheering crowd and he could only watch Monsieur le Prefet in a fever of anxiety.

It was soon dear that Raoul Gregoire was untouched. Evidently the would-be assassin, if he had indeed dispatched one of the poisoned darts, had missed his aim.

Five minutes later Dick and half a dozen detectives were in the garret of the old villa. But they were too late. The bird had flown, badly hurt to judge by the blood which stained the floor. But on the window-sill lay three little poisoned darts ready for use.

A glance at the open skylight in the low roof was enough. In a moment they were out on the roof of the adjoining house.

A few yards away was a rope ladder hooked over the parapet and dangling to the exterior fire-escape leading from the roof of a big drapery store only ten feet below. The miscreant himself had vanished.

The would-be murderer, it was clear, must have climbed the fire-escape during the darkness of the previous night, and lain hidden on the roofs till the procession came along. After the garret had been searched, he had slipped down with impunity while every one was excitedly watching the procession.

They never caught him. But when Gregoire returned to the Prefecture a poisoned dart was found sticking in the upholstery of his car, close to his head. Had it been a bare half-inch lower down it would, no doubt, have struck him with fatal result. Dick's lightning shot had spoilt the miscreant's aim and saved the Prefet's life.

The incident is one of the secrets of the life of official Paris and led to the Prefet's resignation a month later, an occurrence which filled all France with dismay and was the cause of much conjecture and speculation.

Raoul Gregoire has returned to the provinces and is now Prefet of the Department of the Alpes-Maritimes an appointment which he much prefers.

CHAPTER EIGHT.

THE MESSAGE FOR ONE EYE ONLY.

The heat was stifling in the Gran Ancora at Barcelona, an obscure but grandiloquently named cafe of more than doubtful reputation. At dilapidated tables in the long apartment which served as a saloon groups of rough-looking men were drinking steadily. The fumes of strong tobacco poisoned the heavy atmosphere, flies swarmed over everything, the air was full of the reek of stale drink and unwashed humanity.

Though it was but early evening the ill-omened place was already filling up. It was a notorious haunt of betting men and some of the worst characters of the town, frequented by desperadoes who were ready to undertake any deed of violence if it offered the promise of plunder. The swarms of anarchists, who are the curse of Spain, found there a ready welcome and congenial companionship.

At a table at one end of the long room, sat a solitary individual who was reading the "Diario," an anarchist journal devoted to the preaching of doctrine of the most revolutionary type. He spoke to no one, and no one spoke to him, though now and again curious glances were directed towards him. He took no notice of the hubbub around him, but went on calmly reading his paper and sipping slowly at a glass of the villainous wine which seemed to be the favourite beverage of the habitues of the house.

The stranger was no other than Dick Manton. He had come to Barcelona on the trail of a gang of international crooks who had got away with a hundred thousand francs by a clever bank swindle in Paris. Had his identity been suspected his life in that haunt of depravity would not have been worth five minutes' purchase.

But he sat there undisturbed, apparently oblivious of what was going on around him, but in reality keenly on the alert and with one hand close to the butt of the heavy revolver which, as he well knew, he might be called upon to use at any moment in the deadliest earnest.

Manton stiffened suddenly as his eye fell on the queer jumble of figures quoted above. They were buried away in a mass of advertisements and might well be overlooked by the casual reader. As Dick well knew, the "Diario" was used for all kinds of queer communications to all kinds of queer people, and he was attracted by the hint of mystery, a lure which he could never resist. The jumble of figures fascinated him. He had a strange feeling that it would be well worth while to try to decipher the weird cryptogram. But he knew better than to try to do so there. It was not healthy to try in public to pry into the secrets of the underworld of Barcelona.

Dick Manton had had a strange and adventurous career. But as he gazed at the odd announcement, he had a premonition that he was on the edge of a mystery stranger than anything that he had so far encountered.

Having read the queer cryptogram over and over again, Dick slipped the paper into his pocket.

Presently he finished his wine and sauntered out, with an uneasy feeling that made him wonder whether he would reach the door without a bullet in his back. He got out in safety, however, and once clear of the doubtful neighbourhood of the cafe, made his way swiftly to his rooms at the "Hotel Falcon."

It took several hours of hard work before he could obtain the key of the cipher. Then he realised with a gasp that it was in one of the simplest of British signal codes. The key read:

At first Dick was completely mystified. The message conveyed nothing to him. Who were Mataza, Wilson, and Greening? Where was Chalkley? And, above all, why should such a message appear in an English code in an obscure paper published in Barcelona?

It was the last point which worried him most.

He felt instinctively that the message must conceal a meaning of which he was necessarily ignorant, and that it must be related to some affair which was pending in England. The more he thought about it the more uneasy he grew. He had the premonition which so often comes to the help of the detective, and at length, though he was almost ashamed of acting on such slender grounds, he decided to consult his chief. An hour later he was on his way to Paris, leaving the affair of the bank swindlers in the hands of a capable subordinate.

Arriving in Paris he drove straight to Regnier's private apartment, just off the Place de la Concorde.

"Why, Manton, what brings you here?" asked Regnier in surprise. "Have you finished at Barcelona already?"

For answer Dick laid the deciphered cryptogram before the Chief.

"What do you make of that?" he asked abruptly.

Regnier read the slip of paper with knitted brows.

"Queer," he commented. "Why should it be published in the `Diario'? I think it means mischief. Do you know Chalkley?"

Dick shook his head.

"No," he replied, "but it sounds like an English name. And yet I have a feeling that I must have heard it somewhere. It sounds familiar, but I cannot place it. In the meantime I will run home and see if the English papers will tell me anything."

Dick found Jules and Yvette eager for news; he had telegraphed them that he was returning. Dick, Jules, and Yvette had become the most formidable combination in the French Secret Service. They always insisted on working together, they would accept no assistance except that which they chose themselves, and they would work only under the direction of Regnier, who was astute enough to realise their abilities. Yvette had been prevented by a slight illness from accompanying Dick to Barcelona, and both she and Jules, who had stayed with her, hated inaction. There had been a slump in international crime of the kind in which they specialised, and they were suffering from _ennui_. Anything which promised excitement and adventure was welcome.

They listened eagerly while Dick told his story.

"And now," said Dick, half ruefully, as he concluded, "I don't know whether we are on the track of something or whether I have been an idiot."

Yvette's eyes were dancing with merriment.

"Well, Dick," she said, "you are certainly a pretty Englishman not to know one of the most famous places in your own country. Don't you really know Chalkley?"

"No," replied Dick in bewilderment. "What do you know about it?"

For answer Yvette rummaged among a pile of newspapers and produced a copy of the "Times" dated a week before.

"There?" she said. "Read that."

"That" was a closely printed column which Dick proceeded to scan with attention. It was an article describing the wonderful deposits of pitchblende, the ore from which radium is extracted, which had been discovered in the Ural region in the neighbourhood of Zlatoust. An English combine had secured the monopoly of the working for fifteen years, and already a supply of radium valued at one hundred and fifty thousand pounds had been brought home by the famous Professor Fortescue for the use of British chemists and medical men.

The discovery and acquisition of the monopoly by British interests, the article pointed out, had put England far ahead in the field of radium research, for she had now a big supply of the precious commodity at her disposal, while other nations were struggling along with the tiny quantities obtained from other and far less rich deposits. And, as was fully explained, it was not in medicine alone that the radium would be valuable; there was hardly a department of commerce, to say nothing of the arts of warfare, in which radium was not playing a considerable and constantly increasing part. So many new discoveries were being made by the band of experts, of whom Professor Fortescue was the acknowledged head, that it was beginning to be realised that radium in the future was likely to be as valuable as coal and oil had been in the past.

But--and here was the fact of most significance to Dick--the radium was at Chalkley, Professor Fortescue's home in the wilds of the Durham moors. He had taken it there on his return from Zlatoust for use in some critical experiments he had in hand before it was sent on to the young but growing school of Medicine at Durham University.

They had at least approached the heart of the mystery! It was evident that some band of international desperadoes had designs on the precious radium. In spite of their enormous value, the two tubes containing the salt could easily be carried in a man's pocket, and in Germany there would be a ready market for it among the great chemical firms, whose business consciences were sufficiently elastic to permit them to pay a big price and ask no awkward questions.

Dick was reading the report carefully, when he suddenly gave a startled exclamation.

"Why, look here," he said, "the radium is only to be kept at Chalkley till the twenty-ninth. That explains the twenty-nine in the advertisement. And to-day is the twenty-seventh. If anything is to happen it must be at once or they will be too late. I must ring up Regnier." Regnier was with them in half an hour. He was filled with excitement when he learned the facts which Yvette had discovered.

"That," he said, "puts an entirely new complexion on the affair. There can now be very little doubt about the matter. Clearly `lead' means radium, and I think we can interpret `bull market' as an intimation that it is a big prize. They are evidently well informed, whoever they are. We must tell London at once."

But before anything could be done a messenger for Regnier arrived post haste from the bureau of the Secret Service in the Quai d'Orsay with strange news.

A big aeroplane, flying at a tremendous speed, had crossed the Franco-Spanish frontier near Bagneres de Luchon having apparently come right across the Pyrenees. It had ignored all the signals of the French frontier guards, whose aeroplanes had, in consequence, gone up in pursuit. Only one of them was fast enough to approach the stranger, and a fight had followed in which the French machine was crippled and forced to descend. Thereupon the strange machine had proceeded, flying in the direction of Bordeaux. Telephone messages had brought warning of its approach, and several attempts had been made to stop it, but without success. It had been reported, chased by French aeroplanes over Bordeaux, Nantes, and St Malo, and at the latter place, just as dusk was falling, it had left the French coast and laid a course apparently for England. No further news of it had been received.

Regnier looked grave.

"Of course," he said, "we have absolutely no reason to couple this machine with the advertisement in the `Diario,' but I confess I am uneasy. There is at Chalkley radium worth a fortune, easily carried if anyone can get hold of it, and readily convertible into cash. What better device could be employed than a fast aeroplane which could get to Durham and away before anyone could hope to stop it? In any case, I am going to telephone Scotland Yard at once."

Half an hour later he was in communication with Inspector Cummings, the senior officer on duty at the Yard. To him he explained his suspicions, half afraid, with the Frenchman's dread of ridicule, that the other would laugh at his story as an old woman's tale.

But Inspector Cummings was too experienced to be neglectful or sceptical of anything which could disturb Regnier, whom he well knew to be one of the most astute and level-headed of men. He took the matter seriously enough.

"We have heard nothing yet," he said. "But I will 'phone Durham at once and let you know in the course of an hour."

They waited anxiously for the reply. It came at last.

"Cummings speaking," said the voice on the 'phone. "I have spoken to Durham. They have heard nothing there, but they are unable to obtain any reply from Professor Fortescue. The telephone exchange reports his line out of order.

"But here is a queer thing. A big aeroplane, evidently a foreigner, was reported this morning to have been seen over the Midlands flying north. There was a lot of mist about, and we have not been able to trace the machine yet. But it was certainly not one of ours."

"Well," said Regnier, "will you keep me posted? I fancy you will have more news before long. In any case, you will have Durham warned?"

"I have warned them myself," replied Cummings, "and they are sending a couple of men out in a motor to make inquiries. You know Chalkley is about twenty-five miles from Durham and quite in the wilds. Professor Fortescue was, a couple of years ago, carrying out some experiments in which it was absolutely necessary he should be away from anything like traffic vibrations, and he chose this place for the purpose because it was remote from any railway or heavy traffic. He has stayed there ever since; he said it suited him to be `out of the world,' as he called it."

Three hours later came still more startling news.

The police officers who had gone from Durham to Chalkley had found that two armed men had made a raid on Professor Fortescue's house. They had gagged the servants, who were found lying bound and helpless, and the Professor himself was found lying unconscious in his laboratory, having apparently been sandbagged. The raiders had leisurely helped themselves to food, and, having cut the telephone wires, had departed without any particular haste.

But the great leaden safe, weighing several hundredweights, in which the precious radium had been brought to England, was found to have been broken open. _The radium was gone_!

Nothing in the meantime had been heard of the strange aeroplane. But a few hours later an old shepherd walked into one of the local police-stations and told a queer story.

His sheep the previous evening, he reported, had been disturbed by the passing of an aeroplane which, flying very low, had landed on the moors a few miles away from the Professor's house. It had stayed there all night and, so far as he knew, was still there. He had been unable to approach it closely as it was separated from where he had been by a deep gorge and a stream which he could not cross without making a detour of several miles. He had seen two men near the machine who had walked away and disappeared in the folds of the moor.

A strong party of police, Cummings added, had left at once for the spot where the aeroplane had been seen, taking the shepherd with them as guide. The place was remote from any road, and it would be an hour or two before they could get there. But the Air Ministry had been warned, and already aeroplanes were going up in the hope of locating the strange machine.

"I must be in this," said Dick. "Ask him if I can come over. I cannot, of course, go unasked."

"Of course," said Cummings in reply to Regnier's request. "We shall be only too glad to have Mr Manton. Miss Pasquet can come too, if she likes. But I'm afraid he won't be able to get here in time. We shall either have got these fellows or lost them hopelessly in a few hours."

Dick turned to Jules.

"Ring up the British Air Ministry," he said, "and ask them if the strange machine gets off the ground to send us every movement as it is reported. Keep the telephone on all the time. I am going to try to cut these chaps off with the Mohawk. You will have to report to me by wireless every movement as it comes through. From what we have heard I fancy there are very few machines in England fast enough to catch those fellows if they once get started. Of course you will come, Yvette?"

An hour later, Dick and Yvette, seated in the helicopter, were in full flight for England. Yvette was at the controls; Dick, in view of the work that might be before them, crouched over the tiny machine gun which peered from the bow of the machine.

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Professor Fortescue was in a terrible state of distress. He had been working in his laboratory, when a slight noise had caused him to turn round. A man, apparently a foreigner as the Professor judged from the hasty glance he got at him, was standing close behind him. Before the Professor could speak or move he received a violent blow on the head, and remembered nothing more till he recovered consciousness some time later under the care of the police.

His chief concern was for the radium, and his distress at its loss was pitiful. It was a disaster from which he seemed unable to recover. But he appeared to derive a strange satisfaction from the danger in which the thieves would find themselves.

"I don't know how they will get it away," he declared to the police inspector. "It was dangerous to stay very near the safe for long owing to the terrible power of the radium rays. If the thieves try to carry the tubes in their pocket they will not get very far. Surely they cannot realise the terrible risk they are running. However, that need not distress us; all we want is to get the radium back."

In the meantime a strong party of police had arrived from Durham at the Professor's house, and, under the guidance of the old shepherd, started across the moors for the spot at which the strange aeroplane had been seen. It was slow going over rough and difficult ground which tested the endurance even of the younger men. The only unconcerned person was the old shepherd who trudged stolidly on at a pace with which they found it difficult to keep up.

They had gone eight or nine miles before the old man spoke.

"Not far now," he said.

A mile farther on he halted.

"It's just over yon hill," he said, pointing to a small eminence a few hundred yards away. "You will see it as soon as you get at the top."

Breasting the rise, the police cautiously approached the ridge and glanced over. There in the valley, only five or six hundred yards away, was the aeroplane. Two men in air kit stood beside it.

Scattering into a thin line the police rushed down the slope, every man with a revolver ready in his hand.

But they were just too late. They had only gone a few yards when the men hastily took their places in the machine, there was a loud whirr as the engine broke into action, and while the policemen were still a hundred yards away, the strange machine rose into the air and was gone. A furious volley rattled out from the revolvers, but the range was too great and the breathless policemen had the mortification of seeing the machine disappear rapidly to the south.

Immediately the fastest runner of the party started at a trot for the Professor's house to send out a warning. But it was not necessary. The aerodromes all over the kingdom had been warned by wireless from the Air Ministry, and already a host of machines were scouting in every direction.

The stranger, flying due south, had reached Bradford before he was signalled. Instantly there was a rush of aeroplanes from all parts of the Midlands to cut him off. But he slipped through the cordon, flying very high and at a tremendous speed. Outside Birmingham a fast scout picked him up and reported by wireless, and from the huge aerodrome at Cheltenham over twenty fighting planes leaped into the air to stop the career of the marauder.

There was now no chance, at least, of his getting away unobserved. He was under constant observation, alike from the air and the ground, and every moment wireless messages were pouring into the Air Ministry reporting his progress. But to catch him proved impossible. Only two of the pursuing machines were fast enough to keep up with the stranger, and even they could not overtake him. So the headlong flight went on, drawing ever nearer to the southern coast. If the stranger could get out to sea all chance of stopping him would vanish.

But, unknown to the furious British airmen, help was close at hand.

Warned by Jules' wireless messages of the direction the strange machine was taking, Yvette had steered a course to intercept him somewhere in the neighbourhood of Bournemouth, and the Mohawk, with its wireless chattering incessantly, was now swinging lazily at half speed in a big circle between Salisbury and the Hampshire watering-place.

"Over Salisbury now," called Yvette to Dick, her voice ringing out clearly above the muffled hum of the propeller, the only sound which came from the helicopter, with its beautifully silenced engines.

A few minutes later Dick pointed to the north. "Here he comes," he shouted.

Far away were three tiny specks in the sky.

Through his glasses Dick could make them out clearly enough. The leader was a machine of a type he had never seen before; a mile behind it were a couple of planes which he at once recognised as the Bristol fighters which had been so familiar to him in France.

The pace of the three machines was terrific. It was clear the English airmen were going all out in a desperate effort to catch the stranger before he reached the water, and they were expending every ounce of energy. But a moment or two later it was quite clear they were falling behind. Presently a puff of smoke from the leader signalled "petrol exhausted," and he dropped in a long slant to the ground.

The second machine, however, held on grimly, though slowly losing ground. Evidently his predicament was the same as that of his colleague, and a moment later he, too, dipped earthward and was out of the fight.

Only the Mohawk stood between the stranger and safety!

But it was a Mohawk very different from the comparatively crude machine of a year before, wonderful though that was. Dick and Jules had worked out a revolutionary improvement in the lifting screws, with the result that a small supplementary engine, using comparatively little power, was now sufficient to keep the machine suspended in the air. As a result the full power of the big twin driving engines was now available for propulsion, and the speed of the Mohawk, when pushed to the limit, was something of which Dick had hardly dreamed in his earlier days. So far as he knew the Mohawk was easily the fastest craft in existence.

But what of the stranger? Had the men of the mystery craft a still greater secret up their sleeve? That they had something big Dick could plainly see by the way the fastest craft of the British Air Service, the best in the world, had dropped astern of the stranger. Was the Mohawk fast enough to beat the pirate? They would soon know.

As the big machine came on, Yvette set the elevating propellers of the Mohawk to work, and the helicopter shot upward. The stranger saw the manoeuvre and at once followed suit. But here he was at a disadvantage. Yvette's object, of course, was to get above him. He would then be at their mercy, for he could not fire vertically, while the gun of the Mohawk was specially constructed so as to be able to fire downwards through a trap which opened in the flooring. If they could get what in the air corresponded to the "weather gauge" at sea, they would have the marauder at their mercy if the Mohawk had speed enough to hold him. Could they do it?

Plainly the fugitive saw his danger. As Yvette shot upward he must have realised that in speed of climbing he was no match for his antagonist. He decided to trust to his heels.

Yvette, climbing rapidly, had got a couple of thousand feet above the stranger and was heading to meet him. They were now twelve thousand feet in the air.

Suddenly, with a tremendous nose dive, the foreign aeroplane slipped below them. The manoeuvre was so smartly carried out that Yvette was completely taken by surprise, and before she could recover herself the chance of bringing the stranger to battle had gone. He had passed five thousand feet below them, and the issue now depended upon speed and endurance.

With a cry of disappointment, Yvette swung the Mohawk round in pursuit. Their quarry, by his daring manoeuvre, had gained a couple of miles before she could turn, and was fast disappearing towards the sea.

Dick shook his head. He had seen the speed of which the fugitive was capable, and he had the gravest doubts whether the Mohawk could equal it.

Waiting for the strange aeroplane, Yvette had set the Mohawk to a comparatively slow pace. She had misjudged the distance and her error had enabled the raider to get a more than useful--possibly a decisive-- lead.

But even as she swung round she had pressed the accelerator and the Mohawk quivered as the big twin engines began to work up to their maximum. Watching keenly, Dick saw the apparent rush away of the foreigner slacken and finally stop. They were at least holding their own. He signalled Yvette for more speed. She shook her head.

Dick was in despair. The pace at which they were going was not enough. He thought it was their best. But he had not calculated on Yvette's resourcefulness.

The French girl had swiftly made up her mind. She knew they had plenty of petrol for several hours' flight. They were holding their own already in the matter of speed, and the Mohawk, though Dick did not know it, had still some knots in reserve. Yvette would not jeopardise the engines by instantly pushing them to the limit.

But they were "warming up" under her skilful handling. They were two miles behind as they passed over Bournemouth and started the long flight to the French coast which the stranger was seeking.

Half an hour slipped by and Dick suddenly realised that the Mohawk was gaining, slowly, it was true, but unmistakably. He looked inquiringly at Yvette, who nodded and smiled.

"All right, Dick," she shouted. "We can get them any time we want."

Dick realised her plan. His own thought, as a fighting man, would have been to close at once and have it out. But Yvette had the radium in mind. If they smashed the stranger over the sea the priceless radium would inevitably be lost.

With the Mohawk gradually gaining, the chase drew near to the French coast. Cherbourg loomed ahead of them, drew near, and disappeared beneath them. They were over France.

Instantly Yvette began to coax the Mohawk to do its best. Splendidly the engines responded, the plane shot forward at a pace which surprised Dick, and a few minutes later they were directly above the fugitive. The battle was all but won. In vain their quarry sought, by diving and twisting, to shake them off. His position was hopeless.

Seeing a good landing-place ahead Dick fired a couple of shots as a signal. They could see the terrified face of the passenger in the plane below gazing upward at the strange shape of the Mohawk above them.

Then the signal of surrender came, and the fugitive dipped earthward. A couple of minutes later it came to land, and the two occupants stood holding up their hands while the Mohawk came gently to earth fifty yards away, dropping vertically from the sky in a fashion which caused the pilot of the foreign machine the wildest astonishment.

The radium was saved! But it enacted a fearful revenge. The unfortunate passenger, who they found out later was a well-known Spanish anarchist, had imprudently placed the two tubes in his pocket, apparently ignorant of their terrible power. Even in the short time he had them in his possession he was so terribly burned that he died a couple of days later in spite of the efforts made to save him, while the pilot, who had, of course, been near enough to the tubes to get some of the effects, was also so seriously injured that for weeks his life hung in the balance. It was found impossible to remove the tubes to England until Professor Fortescue, overjoyed at the good news, came bringing the leaden safe into which the precious tubes were placed.

The sequel came a week later. Not even the British War Office could ignore the fact that the Mohawk, single-handed, had achieved a feat at which the British Air Force had signally failed. A highly placed official sought Dick out. The result was that the plans of the Mohawk were sold jointly to England and France at the price of one hundred thousand pounds.

And Regnier lost his "star" combination. Dick had no longer before his eyes the fear that had haunted him for so long that in marrying Yvette he would be condemning her to a life of comparative poverty. And so the companionship born amid the stress and tumult of war came at last to perfect fruition in the marriage between the two lovers which took place in Paris just three months after their last air adventure.

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The End.