set?" called Hal.

"All set," was Chester's reply.

"Let her go, then," said Hal, and the single guard who had remained gave the machine momentum with a vigorous push.

The machine moved slowly across the ground at first, then, under Hal's guiding hand, dashed on swifter and swifter. Hal touched the elevating lever and the airplane soared into the air.

Now Chester had been aloft many times, but he had never reached a point where he was not affected by the sensation of the earth dropping away from him. For a moment he clung to the side of the car. His head cleared, in a twinkling, however, and he breathed a sigh of relief.

"All right, Chester," Hal called back, not taking the time to turn his head.

"All right," was Chester's reply. "Step on her, Hal."

Hal obeyed this injunction, and the plane darted in the direction of the distant enemy like a big bird.

There was no light aboard the craft that carried the two lads toward the German lines. On either side, above and below, however, Hal could see now. and then a faint twinkle, indicating that other American craft, bent upon no such dangerous mission as Hal and Chester, still were on the alert to prevent a possible surprise attack by the foe.

These lights were soon gone, however, and now all that Chester could see was the faint outline of Hal's head before him. He looked back, but the last of the American lights had been lost in the distance. Ahead, the German lines were still too far distant for a plane to be distinguishable should it be on guard aloft.

The night was very dark. For this Hal felt thankful, for it meant that, barring accidents and the rays of German searchlights, he had more opportunity of guiding his craft into the enemy lines, unobserved. Could he escape the prying eyes of the foe's sentinels of the sky, he felt that he had nothing to fear.

The distance between the German and allied lines at that point, Hal knew, was less than three-quarters of a mile. This distance was covered in a jiffy, but still Hal kept the nose of the craft pointed due east, for it was his intention to come down well within the foe's lines rather than to risk a landing near the front.

But at last he felt he had gone far enough. His hand tightened on the controls and gradually the speed of the plane slackened. Chester leaned forward, and putting his mouth close to Hal's ears, exclaimed:

"Going down here?"

"Yes," was Hal's reply. "May as well, I guess. It should be as safe as any place. Suit you?"

Chester shrugged in the darkness.

"I'm satisfied if you are," he replied. "Shoot!"

The plane began to descend.

CHAPTER III

AMONG THE ENEMY

The aircraft settled to earth in the darkness as gently as a huge bird and Hal and Chester stepped out silently. For a moment they stood trying to get their bearings.

"Where do you figure we are?" asked Chester in a low tone.

"We should be a mile due east of Sedan," was Hal's reply. "I saw the lights of the city below as we passed."

"Sedan, eh?" said Chester. "What memories of school days that name conjures up, Hal."

"So it does," was Hal's whispered response: "Of Bismarck, of Napoleon III and of the French defeat in the deciding battle of the Franco-Prussian war."

"What a glorious thing it would be if the French could strike a decisive blow at the Germans here now," muttered Chester. "It would be retribution."

"No less," Hal agreed; "and still, to my mind, it would be extremely better if the decisive blow were delivered by American troops, whether at Sedan or elsewhere."

"Right, as usual, Hal," was Chester's reply.

And although neither lad knew it then, it was to be the fortune of American troops to wrest Sedan from the hands of the invader and to be the first forces of democracy to tread the streets of the historic city.

"We've talked enough, Chester," Hal whispered. "It's time for action."

"Let's be on the move, then," Chester whispered back. "Which way?"

"Might as well head toward the city, I guess."

"How about the plane here?"

Hal shrugged in the darkness.

"We'll have to leave it, I guess. If we're not back by morning it will be discovered, of course, and a search instituted for its occupants."

"Which might lead to our discovery," said Chester.

Again Hal shrugged.

"It might, of course," he agreed.

"Then why not pull it in among the trees there?" Chester wanted to know, pointing to a clump of trees a short distance away.

"Not a bad idea," Hal declared. "I hadn't noticed the trees, myself."

"As Stubbs would say, you must be more observing," was Chester's response. "Lay hold here."

With some effort the boys wheeled the plane into the little clump of trees and then stepped forth again.

"It may do," said Hal, eyeing the hiding place carefully in the darkness. "It's invisible enough now, but I don't know how well the foliage will protect the plane in daylight."

"It's the best we can do, at all events," declared Chester. "Come, let's be on our way."

"May as well, I guess," said Hal, and led the way toward the distant city of Sedan.

From time to time the lads passed hurrying figures as they walked along, but they were not so much as accosted. In their German uniforms, they felt reasonably safe, particularly so as their features were concealed by the darkness. Once in the city, however, they knew they would have to exercise greater caution.

Nevertheless they entered the outskirts of the city with firm tread and headed directly toward the center of town. Neither had been in Sedan before and each was conscious of the utter foolishness of prowling around the edge of the city.

"We've got to get among the foe if we want to learn anything," Hal said.

A few lights still twinkled in the city, despite the lateness of the hour. On what appeared to be the main street, the lads made out a fairly large hotel.

"Guess that's our destination," said Chester, pointing.

Hal nodded.

"That's the place," he said, "though I don't know what we'll do when we get there."

"Events will shape themselves," said Chester.

"That's what worries me. If I could shape them according to my own needs and desires it would be much better."

"Don't croak, Hal."

"I'm not croaking. I'm merely