At this one of the aviators raised a hand and the others gathered about him, Frank and Jack with them. All wore khaki clothing and their features were concealed by heavy goggles.

"Careful," whispered the aviator. "A false move and we are discovered.

Spread out now and see what you can learn. Gather here at midnight."

He waved a hand and the Germans, for such Jack and Frank now knew them to be, separated. When the two lads were alone a moment later, Jack said:

"Well, this is what I call a piece of nervy business. What shall we do?

Inform the French commander immediately?"

"No. I have a better plan that that. They can hardly work any mischief tonight. What information they learn will avail them naught for we can warn the French commander later. We must find out what they are up to.

We'll stick close and follow them back to the German lines, if necessary."

"Good, then! Guess we had better do a little skirmishing about. It will keep suspicion from us should we be watched."

"All right," said Frank. "Come on."

CHAPTER VIII

A STARTLING DISCOVERY

With the coming of midnight Frank and Jack returned to the spot where the aeroplanes had been parked. Several of the German aviators already had returned. The man who appeared to be the leader announced that they would await the arrival of the others before taking to the air.

The others arrived one at a time until all were present but two. The machines were in readiness to ascend the moment the missing men arrived. The aviators were at their posts.

Suddenly there came a shout. A moment later the two German aviators who were delaying the departure burst into sight at a dead run.

"Quick!" called one. "We are discovered!"

Immediately the others--Frank and Jack among them--leaped into their machines and soared into the air. The last comers also leaped for their craft and succeeded in getting above ground just as rifles began to crack in the French camp.

Came a sudden cry from the machine nearest that of Frank and Jack. The lads saw a man rise to his feet, throw up his arms and pitch, head foremost, toward the ground. The aircraft, freed of a guiding hand, rocked a moment crazily and then turned over, hurling its other occupant into s.p.a.ce.

There was a cry of anger from aboard some of the other German craft, but no man raised a hand to stay the flight of his car. It would have been suicide and the Germans realized it. They sped away into the darkness whence they had come. Frank and Jack, in their British hydroplane, went with them.

For an hour or two the aeroplanes sped through the darkness at undiminished speed; then the foremost craft slowed down. The others did likewise.

"Surely we haven't reached the German lines already?" said Jack. Frank shrugged his shoulders.

"You know about as much of what is going on as I do," he returned.

"Evidently we are going down, however."

The lad was right.

The leading German plane swooped toward the earth and the others followed its example. A few minutes later all had reached the ground safely and their occupants had alighted.

The two lads glanced around. It was very dark. A short distance to the north they could see the broad expanse of the North Sea, stretching away in the night. The dark waves lapped the sh.o.r.e gently with a faint thrashing sound. The water was very calm.

Except for the figures that had alighted upon the sh.o.r.e in the darkness there was not a human being in sight. To the south, to the east and west stretched miles and miles of sand dunes. Just these sand dunes and the waters of the North Sea--there was nothing else in sight.

At a signal the men gathered around the man who appeared to be the leader. Frank and Jack thanked their lucky stars that the night was very dark, for otherwise they would have been in imminent danger of being discovered; and each lad realized that it would go hard with them should their true ident.i.ties be penetrated.

The darkness served them like a shield. Nevertheless, both lads kept their hands on their revolvers. Each had determined that if discovered, he would make an effort to escape in the nearest of the aircraft. Each knew that there was little hope of such an escape, but, realizing what was in store for them should they be discovered and captured, they had decided it would be better to die fighting than to be stood up against a wall and shot, or, possibly, hanged.

The group of men on the bench became silent as the leader addressed them.

"Men," he said, "it is to be regretted that we have discovered so soon.

There was still work to be done before the hour for our great effort to crush the British fleet. However, to a certain extent we have been successful. We have managed to sow the seed of suspicion in the minds of our enemies. Prisoners, whom we have allowed to be taken, have let slip words that will lead the British to think our fleet will slip from its base and approach England from the south. We know better than that.

We know that on the night of May 31--which is tomorrow--our fleet will strike the British off Jutland."

There was a subdued cheer from the a.s.sembled Germans. The speaker continued:

"Through our efforts the British fleet has been scattered. The main portion of the fleet lies to the south and will be unable to reach Jutland in time to save the portion of the British fleet there from destruction. Of course, should wind of the move reach the British there would still be time for the fleet to gather. But no such word will reach the enemy. After sinking the first section of the British fleet, our vessels will steam south and meet the main British fleet. The numbers will be nearer equal then. We shall be victorious."

Again there was a subdued cheer, in which Frank and Jack joined for the sake of appearances. Again the speaker continued:

"I shall now explain the reason we have landed here. Our part in the work has been done. Here we shall remain until nightfall tomorrow. We shall then sail north and take part in the battle. In my pocket here,"

he tapped the breast of his coat, "are instructions I shall read to you before we leave. Until that time we shall rest here, for we have done work enough for the present. We shall be safe here. Our position now is directly between two French lines and for that reason we shall not be disturbed. Of course, if it becomes necessary, we can take to our machines and get out of harm's way. We have provisions and water enough to last us; and while the weather is warm, it is still cool enough. At any rate, we shall have to make the best of it."

The man ceased speaking and beckoned the others to follow him. He walked a hundred yards to the east. There he made a mark in the sand with his foot.

"Until the time for us to move has come," he said, "let no man set foot beyond that line. I make this rule for safety's sake."

He walked two hundred yards from the sea itself and repeated the operation and instructions; and then to the west.

"Within these bounds," he said, "we will spend tonight and tomorrow.

The man who disobeys these instructions shall be shot. Do I make myself plain?"

There was a murmur of a.s.sent.

"Very well," said the leader. "Now you are all left to your own devices. First, however, I shall pick the watches for the night."

Frank and Jack, at this, slunk well back into the crowd, for they did not wish to be scrutinized closely. But they need have had no fear. The leader of the Germans laid a hand on the shoulders of the two men nearest him.

"You two," he said, "shall stand guard the remainder of the night, one to the southeast and one to the southwest. But do not venture beyond the boundaries I have laid down."

The Germans saluted and moved away.

The leader moved toward the sea and none of the others followed him.

Instead, some walked a short distance to the east, others to the south and still others to the west. They threw themselves down in the sand. A few remained near the airships.

Frank and Jack walked a short distance toward the sea, but kept some distance behind the German leader, who stood looking off across the water, apparently deep in thought. The lads sat down upon the ground.

"Well," said Frank, "what are we going to do about it?"

"Do!" echoed Jack. "Why, there is only one thing we can do--one thing we must do! We must get away from here and warn the fleet!"