When he had finished, he studied thoughtfully the message
which he had transcribed:--

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 deg