There had been a furtive step past the door. Now it returned. We heard a shuffling sound outside, and then two sharp taps with the knocker. Holmes rose, motioning us to remain seated. The gas in the hall was a mere point of light. He opened the outer door, and then as a dark figure slipped past him he closed and fastened it. “This way!” we heard him say, and a moment later our man stood before us. Holmes had followed him closely, and as the man turned with a cry of surprise and alarm he caught him by the collar and threw him back into the room. Before our prisoner had recovered his balance the door was shut and Holmes standing with his back against it. The man glared round him, staggered, and fell senseless upon the floor. With the shock, his broad-brimmed hat flew from his head, his cravat slipped sown from his lips, and there were the long light beard and the soft, handsome delicate features of Colonel Valentine Walter.

Holmes gave a whistle of surprise.

“You can write me down an ass this time, Watson,” said he. “This was not the bird that I was looking for.”

“Who is he?” asked Mycroft eagerly.

“The younger brother of the late Sir James Walter, the head of the Submarine Department. Yes, yes; I see the fall of the cards. He is coming to. I think that you had best leave his examination to me.”

We had carried the prostrate body to the sofa. Now our prisoner sat up, looked round him with a horror-stricken face, and passed his hand over his forehead, like one who cannot believe his own senses.