Surprise on the part of Blake and his chums, as well as on the part of Secor and Labenstein, was so complete that it would be hard to say who felt the sensation most. The moving picture boys, after danger and difficulties, had found the stolen army films and those they believed had taken them. They were about to make a dash and get not only the precious boxes, but also, if possible, capture the two plotters, when, like a bolt from a clear sky, they were themselves called upon to surrender.

"Come on!" yelled Charlie, as he understood the import of the summons to surrender. "We can make a fight for it!"

"Don't try it!" advised Blake. By the light of lanterns carried by the raiding party of Germans he had seen that they were numerous and well armed. It would have been the height of folly to resist, especially as the boys were non-combatants and not entitled to the honors of war.

"Hands up—and search them!" commanded the German officer of the raiding party, as he pointed to Blake and his two chums. He spoke in German and then lapsed into English, which he spoke very well, saying:

"It will be best for you Americans to give in quietly. Hands up!" And the order was stern.

The boys had no choice but to obey, and their weapons were quickly taken from them.

"I will allow you to keep your gas masks for the present," the German captain said, "as you may need them, as we ourselves may, before we get back to our lines."

"Then we are going back with you?" asked Joe.

"Of a certainty—yes! Did you think I would leave you here to go back to your own? Indeed not! Now, then, ready—march—all of you!" and he nodded at Secor and Labenstein.

Blake and his two friends noticed that no hostility seemed directed toward the two conspirators, who, however, appeared as much surprised at the advent of the raiding party as were the boys. It was evident, though, that some understanding existed between the German captain and Labenstein, for they talked in low voices while Secor stood a little apart. The gaze of the Frenchman rested on the boys in what Blake said later seemed a peculiar manner.

"Well, up to your old spying tricks, I see!" exclaimed Joe, with a sneer he could not forego. "Have you summoned any submarines lately?"

A strange look passed over the face of the Frenchman, but he did not reply. Labenstein, who had finished his talk with the German captain of the raiding squad, turned to the boys, and a tantalizing smile spread over his face as he said:

"Ah, we meet again, I see!"

"And you don't seem to have found much use for my flashlight," said Blake. "I hope it still works!"

The German muttered an exclamation of anger, and turned aside to pick up the boxes of films. This was too much for Charles Anderson, who sprang forward, crying:

"Say, those are ours, you Dutch thief! Let 'em alone! We came here to get 'em! Let 'em alone!"

The German captain gave a sharp order, and Charlie was forcibly pulled back by one of the soldiers.

"Say, but look here!" exclaimed the lanky assistant of the moving picture boys. "This isn't war. I mean we aren't fighting you Germans—though we might if we had the chance. We're just taking pictures, and these fellows have stolen our films," and he indicated Secor and Labenstein. The latter made some reply in German to the captain which the boys could not understand.

"Give us back our films and let us go!" demanded Macaroni. "We only came to get them!"

"Enough of this!" broke in the captain. "You are our prisoners, and you may be thankful you are alive," and he tapped his big automatic pistol significantly. "March!" he ordered.

Labenstein and Secor picked up the boxes of exposed film containing the army views and went out of the hut followed by some of the soldiers. Then the moving picture boys were told to follow, a guard of Germans, with ready bayonets, closing up the rear. A little later the boys, prisoners in the midst of the raiding party, were out under the silent stars. For the time peace had settled over the battlefield, extending across the trenches on both sides.

"I wonder what they are going to do with us," said Joe, in a low voice, to Blake.

"Hard to tell," was the quiet answer. "They're marching us toward their lines, though."

This was indeed true, the advance being toward a section of the field beyond the German trenches whence, not long before, had come the searchlights and the hail of shrapnel.

"Well, things didn't exactly turn out the way we expected," said Charlie. "I guess we'll have to make a re-take in getting back our films," he added, with grim humor. "How do you figure it out, Blake?"

The talk of the boys was not rebuked by their German captors, and indeed the captain seemed to be deep in some conversation with Secor and Labenstein.

"I don't know how it happened," Blake answered, "unless they saw us go into that hut and crept up on us."

"They crept up, all right," muttered Joe. "I never heard a sound until they called on us to surrender," he added.

"Maybe Secor and Labenstein saw us and never let on, and then sent a signal telling the others to come and get us," suggested Charlie.

"I hardly think that," replied Blake. "The Frenchman and his fellow German plotter seemed to be as much surprised as we were. You could see that."

"I guess you're right," admitted Joe. "But what does it all mean, anyhow?"

"Well, as nearly as I can figure it out," responded Blake, as he and his chums marched onward in the darkness, "Secor and Labenstein must have hidden the films in the hut after they stole them from the place where we went down under the gas attack. For some reason they did not at once turn them over to the German command."

"Maybe they wanted to hold them out and get the best offer they could for our property," suggested Charlie.

"Maybe," assented Blake. "Whatever their game was," and he spoke in a low tone which could not carry to the two plotters who were walking ahead with the German captain, "they went to the hut to get the films they had left there. And as luck would have it, we came on the scene at the same time."

"I wish we'd been a little ahead of time," complained Macaroni. "Then we might have gotten back with our films."

"No use crying over a broken milk bottle," remarked Joe.

"That's right," Blake said. "Anyhow, there we were and there Secor and his German friend were when the others came and——"

"Here we are now!" finished Joe grimly.

And there, indeed, they were, prisoners, with what fate in store none of them could say.

Suddenly from the darkness a sentinel challenged in German, and the captain of the little party answered, passing on with the prisoners.

A little later they turned down into a sort of trench and went along this, the boys being so placed that each walked between two Germans, who carried their guns with bayonets fixed, as though they would use them on the slightest provocation. But Blake and his chums gave none.

And then, making a sudden turn, the party came to what was evidently an outpost of importance. There were several large underground chambers, fitted up with some degree of comfort and a number of officers and soldiers about. Some were eating, some smoking, and others drinking, and still others sleeping. In one room could be seen a rough table, laden with maps and papers, and there were many electric lights, showing to what degree of perfection the German military system was carried out at this point. A portable dynamo and gasolene engine probably furnished the current.

The captives were halted, and a brief talk in German took place between the captain and the officer to whom he reported. What was said Blake and his chums could not, of course, hear, nor could they have understood had they heard.

A little later, however, they were ordered to march on, and then were shown into an underground room, none too clean and quite dark, and the door was banged shut on them. Just before this they had seen Secor and Labenstein go off in another direction, still carrying the boxes of films.

The echoes of the retreating footsteps of the men who had thrust them into their prison soon died away, and the boys were left to themselves in a veritable cell that was unpleasantly dirty and dark.

"Whew!" whistled Joe, after a moment of silence. "This time we certainly are up against it!"

Suddenly a light flashed in the darkness.

"What's that?" asked Joe sharply.

"I want to see what sort of hotel accommodations they've given us," was Blake's grim answer, as he flashed his pocket light about. The Germans had not taken those from the boys, and they were soon inspecting their prison.

It was merely a hole dug underground, earth, supported by timbers, forming the floor, ceiling and sides, while the entrance was made of a plank door, with cracks large enough to show that a passage ran outside—a passage along which men passed with a frequency which seemed to indicate that escape would be exceedingly difficult.

"Well, we've just got to make the best of it," said Blake. "I'm going to get what rest I can."

It could not be much at best, for there was no furniture in the cavelike cell. The boys curled up in corners—fortunately it was not cold—and thought over their situation. That it was very desperate they all admitted.

That night was like a bad dream to them. At times they dozed off in light slumber, but, as far as they knew, their captors did not so much as look in on them. They did not know, of course, when morning came, but they judged that the sun had risen when, after several hours of waiting, a tin can of water and some food was thrust in to them.

"And I'm hungry enough to eat even German sausage," announced Macaroni, as he inspected the food. It was coarse but satisfying, and the boys felt better when they had eaten it.

Later came a squad of Germans, one of whom spoke enough English to order Blake and his chums to follow them. They were led out of the dungeon, along a covered underground passage, and then they suddenly emerged into daylight.

"Well, it's a comfort to be able to see," remarked Joe, as he and his companions looked about.

Without a word as to where they were to be taken, the boys were marched along, and, for a moment, they feared they were to be the victims of a firing party. But a turn in the course showed them just ahead a group of buildings about which could be seen some German officers.

"Evidently we're going to be questioned by some one in authority," suggested Blake. "Well, that looks more hopeful."

They were at the very edge of an enclosure containing the official headquarters of that part of the German army, and the leader of their squad was about to reply to the challenge of the sentinel when a curious sound was borne to the ears of the boys. It was like a fast motor operating at some distance.

"What's that?" asked Charlie.

As if by a common impulse they all looked up, for the noise seemed to come from above, and they saw dotting the blue sky many small, black specks.

"Aeroplanes!" cried Blake.

The Germans had seen the objects in the air at the same time, but on them the sight produced quite a different effect from that made on the boys.

In an instant all thought of guarding Blake and his chums seemed to have been forgotten. Their escort ran to one side. The sentries on duty before the official headquarters hastened away, and some of the elaborately gold-laced officers ran within the buildings.

A moment later a number of soldiers could be observed some distance away manning a battery of guns, the muzzles of which pointed upward.

"They're going to fire at the airships!" cried Joe.

"And that means they are not German craft!" added Blake. "Boys, I guess the French and Americans are making an airship raid on Mr. Fritz this morning, and maybe it'll be a good thing for us. Let's hunt cover!"