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.