And it had not been an easy part for the French officer to play.  He had, in ways of his own, come to suspect Labenstein, who went under various names, sometimes that of Karl Kooder.  This man, who held forged citizenship papers of the United States, was a German spy and had done much to aid the Kaiser.  But he accepted Lieutenant Secor as a co-worker, on the latter’s representation that he, too, was a friend of Germany, or rather, as the Frenchman made Labenstein think, was willing to become so for a sum of money.  So the two seemingly worked together.

“And it was thus you knew us,” said the lieutenant to the boys.  “Labenstein, to use one of his names, had orders to make all the trouble he could for you when you reached France, and to prevent your getting any pictures, if possible.  Of course he could not do that, but he tried, even to the extent of writing a false note in London that caused your arrest.  I had, seemingly, to help him, but all the while I was endeavoring to find out where the leak was on our side that enabled him to profit.  And I found out.  The leak will be stopped.

“I even seemed to join Labenstein in signaling the submarine, though that night, had he really succeeded in calling her with your light, I would have killed him where he stood.  However, the depth charge solved that question.

“I had to escape from the ship with him to lull his suspicions against me.  Then I went into the German ranks with him, being thought a deserter!  That was hard for me, but I had my duty to perform.

“The rest you know.  It was by a mere chance that Labenstein, when I was with him, came upon your films after the gas attack.  He thought to profit personally from selling them, which is why he did not turn them over at once to his superiors.  Ever since then he has been trying to dispose of them to enrich himself.  And I have been trying to find a way to get them back to you without betraying myself and my mission.

“At last chance favored me.  The big air attack came just after I had secured all the information I wanted.  I was about to go back to my comrades and arrange for the capture of Labenstein if I could.  He still had the films and was about to sell them to another German—­a traitor like himself.

“Then came the big explosion, and he was fatally hurt.  We both took refuge in the tunnel, Labenstein carrying with him the films, and you came just as Labenstein died.  Well, perhaps it is better so.”

“Yes,” agreed Blake, “I think it is.”

“And we have the films back!” exulted Charlie.

“But, best of all, we know Lieutenant Secor is straight!” cried Joe.  “I’d hate to think anything else of him, after he saved our lives.”

“Yes,” agreed Blake softly.

“And now to get back on the job!” cried Joe, after a moment of silence.

And so the moving picture boys again took up their perilous calling.  They soon recovered from their slight injuries caused by the cave-in of the tunnel, and, finding their cameras where they had left them in the French house, resumed the turning of the cranks.