But it was a strange way.  For when the rocks had been pulled down sufficiently to enable them to crawl through, they emerged into a space—­a small room, as it were—­walled with solid logs.  Logs also formed the roof.  It was a room lighted by a lantern, and on a pile of bags in one corner lay a huddled figure of a man.  Standing near him was another man—­a man in a ragged blue uniform—­and at the sight of his face Blake murmured: 

“Lieutenant Secor!”

“At your service!” said the Frenchman, bowing slightly.

“No!” bitterly cried Blake.  “Not at our service—­you traitor!”

The Frenchman seemed to wince, but at that moment a call from the huddled man in the corner attracted his attention.  He bent over him, drew back the covering and revealed in the lantern’s glow the face of Labenstein.

The German raised himself on one elbow, and a wild look came over his face.  His eyes gleamed brightly for a moment.

“They—­they here!” he murmured.  “Well, perhaps it is better so.”

“How better?  What does he mean?” asked Blake.  “Does he think——­”

“Hush!” and the Frenchman spoke softly.  “This is the end—­of Labenstein!” And even as he spoke the man fell back dead.

Lieutenant Secor seemed to breathe a sigh of relief, as though the death of the other had brought a great release to him.

“Now I can speak,” said the officer.  “Now I can explain, and perhaps you will again regard me as a friend,” he said softly.

“Well,” returned Blake, “you probably saved our lives by helping us get out of the tunnel.  But as for being friends with——­”

“Please do not say it,” begged the lieutenant.  “I have had to play a part.  It is over now.  I can again take my place with my comrades and fight openly for France.  For I have learned all his secrets and whence the spy-leaks came.  Now my unpleasant mission is over!”

“What—­what do you mean?” asked Joe, beginning, as did his chums, to have an inkling of the truth.  “Aren’t you two working together against us and for Germany?”

“Never I!” cried the Frenchman.  “I am a member of the French Secret Service, and for months I have consorted with that dog!” and he pointed at the dead man.  “I but played a part to gain his confidence and to learn from what sources Germany was getting her secret information about our soldiers and yours.  Now I know.  I will explain.  But come, we must get out of here.”

“Can we get out?” asked Blake.

“Surely, yes.  The tunnel goes from here into the German trenches, and the other end was not damaged by the explosion.”

“But,” exclaimed Joe, “the German trenches!  We don’t want to go there to be captured again.”

“Have no fear,” said the Frenchman, with a smile.  “I should, perhaps, have said what were the German trenches.  They are now held by some of your own troops—­the brave Americans!”