“I can,” he rejoined quite evenly. “You gave him the soldier’s word of command: ‘File right!’ you said, and I almost looked to see you follow it up with an oath.”

He had me fairly at a standstill. He had quoted my word of warning to Champe precisely, and I doubt not the tone in which it was given suggested the oath which might have capped it. Having nothing more to say, I held my peace, and when the lieutenant had given his rejoinder time to sink in, he came at me again, this time very gravely.

“You are not altogether transparent, Captain Page, nor have you been since the hour you landed in New York. I don’t want to think ill of you, because ill-thinking of a man in your situation could have but one meaning. Now I shall ask you a fair question, and you shall answer it as you choose. Do you—”

I held up my hand.

“First tell me frankly what you know, Mr. Castner, and then I shall be equally frank with you,” I interposed; adding: “at least, as frank as I can be without involving a gentleman who, I am sure, wishes to be charitably unknown in this little controversy of ours.”

His smile was shrewdly triumphant, but it comforted me beyond measure. Whatever he knew, it was not enough to hang me—yet.

“You had a fellow guest in your room last night, Captain; so much any one who passed through the corridor and heard you talking might know. That you kept this guest all night is quite apparent from the fact that he wore your clothes when he went out just now. It may be a very simple little mystery and easily explained; but, as I said before, mysteries are dangerous things, Captain—for you.”

Now I knew who had bored the hole in the wall of the unoccupied room next to mine and why it had been bored. Castner had wished to see the face of the man whom I was keeping over night. Remembering how hard it would be to see anything definite through a quill-sized hole in a thick partition wall, I took a chance that Castner was still in doubt as to my roommate’s identity. And so long as I could keep this in the dark, there was hope.

“There is no great mystery about it, Mr. Castner, and nothing to conceal save the gentleman’s name and standing. Before I attempt to explain, may I ask if you know anything of General Arnold’s domestic affairs?”

He shook his head.