Plans for attack on La Guir communicated.  Attack foiled.  Believe Smith in London.

“Anything important, sir?” the young man at the typewriter asked.

Thomson nodded but made no immediate reply.  He first of all carefully destroyed the message which he had received, and the transcription, and watched the fragments of paper burn into ashes.  Then he replaced the code-book in the safe, which he carefully locked, and strolled towards the window.  He stood for several minutes looking out towards the Thames.

“The same thing has happened again at La Guir,” he said at last.

“Any clue?”

“None.  They say that he is in London now.”

The two men looked at one another for a moment in grave silence.  Ambrose leaned back in his chair and frowned heavily.

“Through our lines, through Boulogne, across the Channel, through Dover Station, out of Charing-Cross, through our own men and the best that Scotland Yard could do for us.  In London, eh?”

Thomson’s face twitched convulsively.  His teeth had come together with a little snap.

“You needn’t play at being headquarters, Ambrose,” he said hoarsely.  “I know it seems like a miracle but there’s a reason for that.”

“What is it?” Ambrose asked.

“Only a few weeks after the war began,” Thomson continued thoughtfully, “two French generals, four or five colonels, and over twenty junior and non-commissioned officers were court-martialled for espionage.  The French have been on the lookout for that sort of thing.  We haven’t.  There isn’t one of these men who are sitting in judgment upon us to-day, Ambrose, who would listen to me for a single moment if I were to take the bull by the horns and say that the traitor we seek is one of ourselves.”

“You’re right,” Ambrose murmured, “but do you believe it?”

“I do,” Thomson asserted.  “It isn’t only the fact of the attacks themselves miscarrying, but it’s the knowledge on the other side of exactly how best to meet that attack.  It’s the exact knowledge they have as to our dispositions, our most secret and sudden change of tactics.  We’ve suffered enough, Ambrose, in this country from civil spies—­the Government are to blame for that.  But there are plenty of people who go blustering about, declaring that two of our Cabinet Ministers ought to be hung, who’d turn round and give you the life if you hinted for a moment that the same sort of thing in a far worse degree was going on amongst men who are wearing the King’s uniform.”

“It’s ugly,” Ambrose muttered, “damned ugly!”

“Look at me,” Major Thomson continued thoughtfully.  “Every secret connected with our present and future plans practically passes through my hands, yet no one watches me.  Whisper a word at the War Office that perhaps it would be as well—­just for a week, say—­to test a few of my reports, and they’d laugh at you with the air of superior beings listening to the chatter of a fool.  Yet what is there impossible about it?  I may have some secret vice—­avarice, perhaps.  Germany would give me the price of a kingdom for all that I could tell them.  Yet because I am an English officer I am above all suspicion.  It’s magnificent, Ambrose, but it’s damnably foolish.”