He wondered if his plan would work, and if he would be able to carry it out. If, in the final test, would he dare to do what he had tried to arrange? Time enough to think of that when the moment for decision came.

And meanwhile there were a hundred things that might happen to ruin his plan. There was nothing to do now but wait. But every moment of waiting brought the climax nearer. The hum of the motors of the airships rose louder on the quiet air, broken only by the faint and distant mutter of the battle that was still being fought miles away. It sounded now like the buzzing of a swarm of bees, magnified a thousand times. And then the field was full of men, rushing from the inn. He wondered how they could have been concealed there. But such wonder was idle, and he did not think of it. Instead he watched keenly. First one monstrous aerial battleship came to rest on the earth. At once the men in the field surrounded her, seizing the ropes that were flung out, and made her fast.

There was a good deal of noise. Men were calling in German of course.

But soon order was restored, and the only voices were those giving commands. Suddenly Frank's face lighted up.

"Did you understand, Henri?" he said. "The men in the field are to be the crews for the fighting. They have sailed here with only enough men to steer them. And now all are ordered out, to stretch their legs!"

"Yes, I heard that order," said Henri.

"Now keep your eyes glued to them. What are they doing?"

They listened and watched intently.

"Just as I thought," said Frank. "See, they are going to fill the tanks.

There, they are attaching hose. And they have a pump--they surely must have a pump, to send the petrol uphill!"

Meanwhile the other airship had come down, on the other side of the barrels, and there as nearly as they could judge, the same procedure was carried out.

"Watch, Henri! Are they pumping?" cried Frank.

"Yes!" said Henri. "Now--now--now is your time, Francois!"

Frank hesitated the fraction of a second.

"If it meant killing them, I could not do it," he said, solemnly. "But they are all out of the airships. Now!"

On the word he closed the circuit he had made by connecting the loose ends of the wire he had carried from his petrol filled hole to the two batteries he had brought from the car. He had broken the circuit at the other end, leaving the two wires separated by the fraction of an inch, and cunningly held in place. The result was a spark--or would be, if he had not erred.

And he had made no mistake! For as he closed the circuit, he saw a flash of flame at the spot where he and Henri had dug the hole into which the petrol had flowed from the barrel they had opened. The spark had fired the explosive gas that results when petrol is mixed with air.

The flame ran along the shallow trench, and, amid a chorus of shrieks from the Germans who scattered in all directions, the fire reached the barrel. In a moment there was a loud explosion. The flame flew to the other barrels--the whole neighborhood of the barrels, owing to the mixture of the petrol and the air, was then filled with an explosive and inflammable gas.

There was a great flash of flame, broken by a dozen sharp reports as one barrel after another blew up.

And still, though the Germans were flying in all directions, plainly visible in the light of the blazing gasoline, the real success of Frank's plan hung in the balance. But then what he had calculated happened. The flame ran through the lines of hose. And a moment later two great shafts of flame marked the spread of the fire to the helpless monsters of the air. There was no chance to save them. Indeed, even the Germans had no other thought than to save their own lives. Their raid, whatever its ultimate object, was ruined and two vessels of the great air fleet of the Kaiser were destroyed.

For a moment after the final catastrophe the two scouts stayed, caught by the wonder and the magnificence of the ruin they had wrought. But then Frank cried out,

"Come on! We haven't a moment to lose! They'll know that that was no accident! Some came running this way. They'll find the wires! And then they'll know. The wires will bring them here. Hurry!"

They began running desperately toward the automobile.

CHAPTER XVII

THE ESCAPE

Their one chance of escape, as they both realized fully, was to get back to their automobile before the Germans recovered themselves sufficiently to begin searching for those who had brought such swift and terrible disaster upon their enterprise. And so they made no effort to move quietly or secretly now. To do so would have meant delay and delay was what they could not afford. The distance seemed far greater than when they had first traversed it. It seemed that they would never pa.s.s the house which the Germans had used as a base. But finally they reached it.

And as they did so a door burst open, and they saw a light within.

A man, with the cap of a German officer, though otherwise he wore civilian clothes, came rushing out, tugging at his pistol. He had heard them running. By some bad chance, then, there had been a man--a German--left in the inn!

"Stop!" he cried, furiously.

But they kept on running. He could not see them, dazzled as he was by coming from the lighted house into the deep darkness of the road. But he was in front of them, and they slowed up, instinctively, though they still ran. And then they came into the light of the door. He started back.

"Kinder!" he cried. "Children!"

It was the exclamation of the Uhlan who had stopped them in the afternoon. But now it was uttered in a vastly different tone. The German was beside himself with rage. Perhaps he had had some heavy share of responsibility for the safety of the Zeppelins. But whether that were so or not, he was plainly maddened by the sight of the boys. He could scarcely have understood how completely they were responsible, but the way they were running and the direction whence they came proved only too clearly that they had had some hand in it.

"Stop, Henri!" cried Frank, suddenly. "We can't get away. We surrender!"

They stopped. Frank was obeying the order Major Cooper had given him.

Perhaps, had he been alone, he would have risked a further attempt to escape. But there was no doubt that the German meant to shoot, and he could not expose Henri to the risk.

They stopped full in the path of light that came from the open door of the inn. Behind them, in the road, voices were raised. It was plain that their wires had been followed, and that others were in pursuit. And, after all, Frank felt they could afford to grin at being made prisoners now. They had accomplished a great feat. Even if they were caught, that was to their credit.

And then suddenly he gave a cry of horror. Henri was a little ahead of him for he had not been able to stop as abruptly as Frank. And the German officer, too furious, perhaps, to think of what he was doing, raised his pistol and fired point-blank at the French boy! He fired--but there came from his pistol not a sharp report, but only the dull click as the hammer fell. Twice more he pulled the trigger. But something was wrong. He had made a fatal error--his revolver was unloaded.

But it was only by the luckiest of accidents that Henri was still alive.

Frank had seen the murderous attempt, and now rage mastered him for the moment.

"You coward!" he shrieked. He flung himself at the German officer, who was trying frantically to get at his cartridges. So sudden was the attack that he was taken utterly by surprise. Before he could defend himself, Frank was wrenching his arm. A moment more, and the German officer squealed like a frightened pig, for Frank had succeeded in getting a hammer lock on him. He pulled at the revolver with his other hand, and at last the German, to escape a broken arm, had to loosen his grip. Even a weakling can cripple the strongest man if he once gets that hold. And Frank, in his rage at the cowardly thing he had seen, was almost a match for the full grown man in any case.

As soon as he got the revolver he let go of the German's arm. But before the officer could move, Frank had clubbed the pistol and struck him sharply on the head. He went down like a log.

"Run, Henri, run!" he cried. "They're coming up behind us! Run for the car!"

Behind them, indeed, the footsteps of running men were plainly to be heard. A shot rang out, but both boys had turned instinctively to the side of the road and were running low in the ditch beside the highway.

They could not be seen, and the firing ceased. It seemed that most of the men were unarmed, or carried revolvers at the most. Had there been rifles behind them, they would have had no chance. But as it was, they reached their car and leaped in. Henri threw the switch of the electric starter, the motor leaped into throbbing life, and they were off.

Behind them more shots were fired, but the aim was wild. And they sped away, at fifty miles an hour, pursued only by a few vain revolver bullets, and by a chorus of shouts and yells of rage and execration.

"The coward!" stormed Frank. He had never been so angry in his life. "He might have killed you, Harry! And just because he was in a rage over what had happened to the airships! He didn't even know that you'd had anything to do with it--not positively! And we'd already surrendered."

Henri laughed--and he meant the laugh. It was not affectation. He had faced his danger in the true spirit of the Frenchman, who is as brave in action as any man in the world.

"Eh, well!" he said. "He did not shoot me, so what does it matter? That was a fine crack on the head you gave him! He will remember us, I think, next time he sees us."

Frank shuddered a little.

"I hope not!" he said. "Or, that if he does, he will be a prisoner himself, and won't be able to try to get even."

Frank remembered the look of sheer devilish rage in the eyes of the German. It was not pleasant to think that they might meet again.

"If it is to be, it will be," said Henri. "I bear him no grudge! He had cause to be angry--ma foi, yes! The Kaiser will not say pretty things when he hears of what we did to-night, Francois!"