“What, indeed? It is art for art's sake, Watson. I suppose when you doctored you found yourself studying cases without thought of a fee?”

“For my education, Holmes.”

“Education never ends, Watson. It is a series of lessons with the greatest for the last. This is an instructive case. There is neither money nor credit in it, and yet one would wish to tidy it up. When dusk comes we should find ourselves one stage advanced in our investigation.”

When we returned to Mrs. Warren's rooms, the gloom of a London winter evening had thickened into one gray curtain, a dead monotone of colour, broken only by the sharp yellow squares of the windows and the blurred haloes of the gas-lamps. As we peered from the darkened sitting-room of the lodging-house, one more dim light glimmered high up through the obscurity.

“Someone is moving in that room,” said Holmes in a whisper, his gaunt and eager face thrust forward to the window-pane. “Yes, I can see his shadow. There he is again! He has a candle in his hand. Now he is peering across. He wants to be sure that she is on the lookout. Now he begins to flash. Take the message also, Watson, that we may check each other. A single flash—that is A, surely. Now, then. How many did you make it? Twenty. Do did In. That should mean T. AT—that's intelligible enough. Another T. Surely this is the beginning of a second word. Now, then—TENTA. Dead stop. That can't be all, Watson? ATTENTA gives no sense. Nor is it any better as three words AT, TEN, TA, unless T. A. are a person's initials. There it goes again! What's that? ATTE—why, it is the same message over again. Curious, Watson, very curious. Now he is off once more! AT—why he is repeating it for the third time. ATTENTA three times! How often will he repeat it? No, that seems to be the finish. He has withdrawn form the window. What do you make of it, Watson?”