He then made a very careful examination of the drawers of the washstand. Crossing the room to the left-hand window, a round stain, hardly visible on the dark brown carpet, seemed to interest him particularly. He went down on his knees, examining it minutely⁠—even going so far as to smell it.

Finally, he poured a few drops of the cocoa into a test tube, sealing it up carefully. His next proceeding was to take out a little notebook.

“We have found in this room,” he said, writing busily, “six points of interest. Shall I enumerate them, or will you?”

“Oh, you,” I replied hastily.

“Very well, then. One, a coffee-cup that has been ground into powder; two, a despatch-case with a key in the lock; three, a stain on the floor.”

“That may have been done some time ago,” I interrupted.