“Before my time,” said Billy. He drew the window curtains apart and looked out into the street. “There are folk who watch us from over yonder. I can see a fellow now at the window. Have a look for yourself.”

Watson had taken a step forward when the bedroom door opened, and the long, thin form of Holmes emerged, his face pale and drawn, but his step and bearing as active as ever. With a single spring he was at the window, and had drawn the blind once more.

“That will do, Billy,” said he. “You were in danger of your life then, my boy, and I can’t do without you just yet. Well, Watson, it is good to see you in your old quarters once again. You come at a critical moment.”

“So I gather.”

“You can go, Billy. That boy is a problem, Watson. How far am I justified in allowing him to be in danger?”

“Danger of what, Holmes?”