“But you might have told Colonel Ray and the Duke separately,” I remarked.  “The Duke has never been my friend, and Ray has other causes for being angry with me just at present; but between them they rescued me from something like starvation, and it is terrible for them to think of me as they are doing now.”

Lord Chelsford poured himself out a glass of wine, and held it up to the light for a moment.

“Mr. Ducaine,” he said, “a secret is a very subtle thing.  Though the people who handle it are men of the most unblemished honour and reputation, still the fewer they are, the safer the life of that secret.”

“But the Duke and Colonel Ray!” I protested.

“I might remind you,” Lord Chelsford said, smiling, “that those are precisely the two persons who shared with you the knowledge of the word which opened the safe.”

I laughed.

“I presume that you do not suspect either of them?” I remarked.

“The absurdity is obvious,” Lord Cheisford answered.  “But the force of my former remark remains.  I like that secret better when it rests between you and me.  It means, I know, that for a time—­I promise you that it shall be only for a time—­you must lose your friends, but the cause is great enough, and it should be within our power to reward you later on.”

“Oh, I am willing enough,” I answered.  “But may I ask what you are going to do with me?”

Lord Chelsford smoked in silence for several moments.

“Mr. Ducaine,” he said, “who is there in the household of the Duke who opens that safe and copies those papers?  Who is the traitor?”

“God only knows!” I answered.  “It is a hopeless mystery.”

“Yet we must solve it,” Lord Chelsford said, “and quickly.  If a single batch of genuine maps and plans were tampered with, disparities would certainly appear, and the thing might be suspected.  Besides, upon the face of it, the thing is terribly serious.”

“You have a plan,” I said.

“I have,” Lord Chelsford answered calmly.  “You remember Grooton?”

“Certainly!  He was a servant at Braster.”

“And the very faithful servant of his country also,” Lord Chelsford remarked.  “You know, I believe, that he was a secret service man.  He is entirely safe, and I have sent for him.  Now I imagine that the Duke will wish our new secretary to live still at the ’Brand’—­he preferred it in your case, as you will remember.  Our new secretary is going to be my nephew.  He is very stolid and honest, and fortunately not a chatterbox.  He is going to be the nominal secretary, but I want you to be the one who really does the work.”

“I am afraid I don’t understand!” I was forced to admit.

“It will mean,” Lord Cheisford said, “some privation and a great deal of inconvenience for you.  But I am going to ask you to face it, for the end to be gained is worth it.  I want you also to be at the ‘Brand,’ but to lie hidden all the day time.  You can have one of the upstair rooms fitted as a writing room.  Then you and my nephew can do the transposition.  And beyond all that I want you to think—­to think and to watch.”