"Did you see something very strange about that bed?" Holmes asked. "It could not be moved, because it was fixed to the floor. Did you ever see a bed like that before?"

"I cannot say that I have."

"The lady could not move her bed. It must always be next to the ventilator and to the rope. We can call it a rope, since it was clearly never meant to be a bell-pull."

"Holmes," I said, "I am beginning to understand what you are telling me. We are only just in time to stop some clever and horrible crime."

"Clever enough and horrible enough. When a doctor becomes bad he is a very bad criminal. He is brave and he knows what to do. I know two doctors who were very bad men. Dr Roylott may be even worse, but I think, Watson, that we shall be more clever than he is. We shall see many horrible things this evening. But now let's relax and talk for a few hours about something more happy."