building, and this was immediately opposite the large street door. When one entered from the street one ascended three or four broad marble steps, pushed open one of a pair of glazed swing doors and found oneself facing the door by which Mr. Deacon entered and left his quarters. There had originally been other doors into the corridor from some of the rooms, but those Mr. Deacon had had blocked up, so making the flat entirely self-contained. Just by the glazed swing doors which I have spoken of, and in full view of the old gentleman's door, the hall-porter's box stood. It was glazed on all sides, and the porter sat so that Mr. Deacon's door was always before his eyes, and, so long as he was there, it was very unlikely that anybody or anything could leave or enter by that door unobserved by him. It is important to remember this, in view of what happened on the occasion I am writing of. There was one other exterior door to Mr. Deacon's flat, and one only. It gave upon the back spiral staircase, and was usually kept locked. This staircase had no outlet to the corridors, but merely extended from the housekeeper's rooms at the top of the building to the basement. It was little used, and then only by servants, for it gave
