As they left the village the two companions, who seemed quite old friends already, quickened their pace to a run.

"My observer is in there," said the French pilote aviateur, pointing to an isolated cottage as they passed it. "It would be cruel to tell him that I have already found a fresh comrade. The good news shall keep until we return. And now, cher ami, we have no time to lose, as we have only something like four hours of darkness before us, and we must be well on the way back when daylight breaks."

"How far is it to the Zeppelin den?" inquired Dennis, as they turned aside through a cornfield.

"About two hundred kilometres," replied the pilot. "A trifle more than a hundred of your English miles. VoilÀ, there she lies—a brand-new Aviatik, and that is my machine over there."

"How did you succeed in bringing the German down without injury?" asked Dennis, as they reached the biplane, which loomed large and weird in the twilight.

"More by good fortune than anything else," said Lieutenant Laval modestly. "You see, first of all I killed his observer with a lucky shot from my mitrailleuse and wounded the pilot himself. It was death or capture for him—it proved to be both. My machine—a Voisin—was one of the best, and, finding it impossible to escape, the Hun certainly made a very fine descent. He must have died at the moment the 'plane came to ground. And that reminds me—our success will depend on our masquerading as Germans, and we must use their clothing; they are both here."

There was a tinge of gravity in his voice as he led the way to some bushes a few yards off, where, stretched out side by side, lay two dead men with a mackintosh spread over them.

"They were brave, although they were Boches," said Laval. "And you will see that one of them is wearing an Iron Cross; I have not disturbed it."

In a few minutes they had removed the leather jackets lined with sheepskin from the two aviators.

"Henceforward we had better speak entirely in German, you and I; it will be good practice in case we require to use it," said Laval. And when they had equipped themselves they climbed up, and the Frenchman explained the compressed-air starting-gear and the various methods of control to Dennis.

"You must know these things," he said, with a smile, "so that you can take charge if anything happens to me; but these are first-rate machines, and with their dual ignition and the two separate carburettors they tell me there is very little engine trouble with them. However, my friend, we are about to see what we are about to see."He glanced at his watch in the rapidly fading light.

"For some reason observer and pilot sit back to back," said Laval. "But you can slue your seat round and work your gun from the right if you like. You will find everything ready for use, signalling lamp and a fine map." And with a blue pencil he marked off the course they were about to take and the various landmarks, for which a sharp look out must be kept.

Then the whir of machinery cut off all possibility of further conversation; Dennis gazed round at the darkening landscape as Laval released her, and after a short run forward over the grassland the Aviatik began to rise.

So far, Dennis had not counted the cost of his adventurous expedition, or the by no means remote possibilities of his being captured and sent to terrible Ruhleben. He had only seen the dash and daring of it all, and now he could only see the velvety blackness that lay thousands of feet beneath, where the earth was.

Once from very far below them the boom of guns made itself heard, even above the flogging of the engines and the whir of the tractor in front of him, and his pilot handed back a scrap of paper on which he had scrawled some words.

Switching on his torch Dennis read: "We are crossing our own lines now. That light away to my left is Metz. We are over Lorraine, and I am going to turn south-east."

Through his glasses Dennis could see a dull glow in the distance, which was soon left behind as Laval altered the course, and for some time their flight was through cloud-banks which hid everything.

After a while the pilot passed him another message. "Look down; we cannot be far from the Rhine now, and it is important to know when we cross it. Keep a sharp look out."

The depression of the point of the nacelle told Dennis that the Aviatik was planing down to a lower altitude, and when, some distance ahead, he saw the milky gleam of a river winding away to right and left, he hung over the side with the powerful German glasses glued to his eyes.

The moment it passed beneath them he touched Laval on the shoulder, and, swinging round again to the right, they flew almost due south, still coming down lower and lower.

It was a clear night, and the visible difference in the blackness of the ground here and there told Dennis that they were traversing above mountainous country, while the little bright specks shining like glow-worms marked the existence of enemy towns and villages, whose inhabitants fancied themselves secure from the daring French airmen.

With the exception of the historic raid upon Karlsruhe they had seldom journeyed so far afield.

For a moment the engines ceased working, and Laval shouted to his companion: "We must be close to the place now. There should be a hill covered with pine trees in front of us, and the hangar lies within a league beyond it on a flat plain.""Then yonder it is!" cried Dennis. "There is no end of a strong light showing ahead. That ragged edge that looms against it must be your tree tops."

"Good!" replied the pilot. "Get your bombs ready. When I shut off again we shall be as nearly above the spot as one can judge."

He restarted the engines. In the distance a curious yellow glow outlined the hill, and as they sailed clear of the pines the glow resolved itself into a considerable illumination, for which the pilot steered.

Rows of electric lamps formed a huge parallelogram, in the centre of which was a long black object, undoubtedly the airship hangar.

"By Jupiter!" yelled Dennis; "we're in luck to-night! The Zeppelin's coming out!"

He forgot that his words were completely drowned, and he received a sudden shock when the brilliant beam of a searchlight flashed up from the ground, and, after a circling swoop, found them and held them in its fierce eye. Every stay and rivet was as clearly visible to him as though it had been noonday, and it was a trying moment.

As another light challenged them, and asked "Who are you?" he remembered Laval's previous instructions, and showing his signal lamp, replied in the Morse code, "Blumberger, returning from reconnaissance beyond MÜlhausen."

Blumberger was lying dead under the mackintosh in the cornfield near Bar-le-Duc, and Dennis was wearing his outer garments; but the message had been understood, and was followed by the command: "L30 coming out now. Be careful until all is clear; then report, Blumberger!"

"Yes, we will be very careful!" muttered Claude Laval, who had read off the message at the same time; and flying slowly at scarcely more than five hundred feet above the ground he steered towards the hangar.

Out of the giant shed the great grey nose of the Zeppelin came gliding into view, shining like some silver thing in the light of the electric lamps, the army of men who guided its movements looking like so many busy ants as the searchlights switched off the Aviatik and focused on the airship, evidently for their own guidance.

Suddenly the Aviatik dipped, and Laval made a gesture with his helmeted head. There was no Rolland releasing apparatus fitted to the machine, and the Frenchman's ten bombs were ranged on either side of the observer.

He knew the moment had come, and with a rapid movement Dennis flung them over into space! As the sixth left his hand he felt the machine begin to mount steeply as Laval opened the throttle and put the engines to their fullest power, and the remaining four death-dealing missiles were dropped out at random.

Peering down over the edge, three tremendous explosions reached their ears, followed by another and another; and then everything was drowned in the mightiest explosion of them all, as Zeppelin and hangar burst into a sheet of flame.

Wider and wider it spread, and higher it rose, a great red and yellow roar of lapping tongues, sometimes hidden by dense black smoke, only to flare out brighter than before.And still the raider climbed at a perilous angle, and at such a speed that Dennis gave up all attempts to use his glasses.

As he clung with one hand to a gun bracket, looking giddily down, something screamed past the aeroplane, missing the wings by only a few feet, and a shrapnel shell burst overhead.

"I thought 'Archibald' would have something to say to us," muttered Dennis, as Laval banked away to the right, still rising. "Hallo! Now they've got us!" And three brilliant beams shot into the night sky, one of them focusing the Aviatik and the two others instantly joining it, to show the anti-aircraft gunners their target.

Laval dived—a breathless, daring swoop down—as two shells burst above their heads; but, quick as he was, a shower of bullets rained through one of the wings. Dennis could see the holes when the searchlights got them again, and the side of the fuselage was pitted with dents.

Right and left, above and below, in front and behind them, the whole sky was suddenly alive with shell bursts; and into the observer's brain came the recollection that he had an interview with General Joffre at eight o'clock that morning! He found himself actually smiling at the thought, and wishing that he could speak to the man in front of him—the helmeted man with rounded shoulders bent over his wheel, who pressed levers and bent the control pillar this way and that, as he sent the biplane zigzagging through the heavens with a suddenness that bumped Dennis about, and threatened more than once to fling him out into eternity.

He did not feel the cold, although it was intense; and he had the presence of mind to pass a strap round his waist and fasten himself in. And then he crouched there, marvelling at their luck and the iron nerve of his companion, who, so far, was responsible for their escape.

He knew that they were already a long way from the blazing airship which they had destroyed, and a feeling of exultation took possession of the lad. They were going to win through—they would do it yet; it was written that they were to get free, and he closed his eyes, giddy with the whirl of mingled emotions that filled him.

They had eluded the searchlights for a moment, but another screaming shell overtook them, and as it burst he opened his eyes, and saw Claude Laval sink forward and huddle up on top of his wheel.

"By Jingo, they've got him!" gasped Dennis, sickening with fear for the first time; but recovering himself on the instant, he flung off the strap and reached forward in an attempt to get to the wounded Frenchman without any very distinct idea of what he could do if he succeeded.

But Laval, as though he had read his thoughts, straightened himself and gave a jerk with his head, at the same time sending the machine earthward in a nose dive at an appalling angle.

Dennis clung to the front of the circular cockpit which was the observer's post, and again his eyes closed as the downward rush took his breath away.

"Poor little mater!" And there was a world of agony in the boy's thought, interrupted by finding himself precipitated backwards in a heap, as the nacelle lifted and the dive was checked.

Only for a moment, however, for down they shot again, the downward course being a harrowing succession of switchback curves, which ended in a curious silent glide on even keel, a terrific jolting and a dead stop.

"Are you there?" said an odd, far-away voice, as Dennis slowly gathered himself up with a sigh of heartfelt relief.

"Yes, I'm here. You don't mean to say we're actually on the ground and safe!" he cried hoarsely.

"Hush! Do not speak too loud!" groaned Laval. "We are as safe as we can be on German soil, but I am afraid my right shoulder is broken; and worse still, the engines stopped of their own accord before we made that last dive."

Dennis, as soon as he had recovered from the species of partial paralysis which had taken possession of his limbs, climbed forward to his companion, who rested his head against his shoulder for a moment, and groaned faintly through his clenched teeth.

"That was magnificent, Laval!" whispered Dennis. "Where is the flask of cognac? Here, drink this!"

"Thanks, my dear friend," murmured the wounded Frenchman. "Do not worry about me. It is a question of what is wrong with the Aviatik. There is just one hope for us. Look at the petrol tank. Oh, you can use a light, for, remember we are Germans now if anyone comes along."

Torch in hand, Dennis examined the petrol tank carefully, and his voice shook with renewed hope."The tank is untouched," he reported. "But there is only an inch of spirit left at the bottom of it. That's the trouble. There is something like a house yonder among the trees. What do you say?"

"There is only one thing to be said, my dear Blumberger," replied Laval, with a faint smile. "We must commandeer petrol without delay. I find my arm is not broken after all, but I am bleeding like a pig. It is running into my boot. Help me out, and we will see what the good people over there can do for us."

"Have you any idea where we are?" queried Dennis, as he assisted his wounded companion to the ground with some difficulty.

"Somewhere in the Black Forest," replied Laval. "And unfortunately not much more than ten miles, scarcely that, from the Zeppelin shed. They will search for us, never fear; they are searching now! Moreover, it will be daylight directly, and it is necessary that we hurry ourselves if you want to keep your appointment."