Warren further shows that the enemy, whoever they are, are
themselves not aware of the substitution of the female lodger for
the male. It is very curious and complex, Watson."

"Why should you go further in it? What have you to gain from
it?"

"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