"I wrote two more articles and then, feeling more drowsy than ever, I rose and walked up and down the room to stretch my legs. My coffee had not yet come, and I wondered what was the cause of the delay could be. Opening the door, I started down the corridor to find out. There was a straight passage, dimly lighted, which led from the room in which I had been working, and was the only exit from it. It ended in a curving staircase, with the commissionnaire's lodge in the passage at the bottom. Half way down this staircase is a small landing, with another passage running into it at right angles. This second one leads by means of a second small stair to a side door, used by servants, and also as a short cut by clerks when coming from Charles Street. Here is a rough
chart of the place."
"Thank you. I think that I quite follow you," said Sherlock Holmes.
"It is of the utmost importance that you should notice this point. I went down the stairs and into the hall, where I found the commissionnaire fast asleep in his box, with the kettle boiling furiously upon the spirit-lamp. I took off the kettle and
