“How do you know that?” Ringwood asked.
“You'll see later. Now X went up to the front door and rang the bell. The maid came along, recognised X. . . .”
“How do you know that?” Ringwood repeated.
“I don't know it. I’m just giving you the hypothesis you asked for. I don't say it's correct. To continue: this person X inquired if Silverdale (or Mrs. Silverdale, perhaps) was at home. Naturally the maid said no. Most likely she told X that her companion had scarlatina. Then X decided to leave a note, and was invited into the house to write it. It was a long note, apparently; and the maid was told to go to the kitchen and wait till X had finished. So off she went.”
“Well?”
“X had no intention of putting pen to paper, of course. As soon as the maid was out of the way, X slipped upstairs and switched on the light in this room.”
“I'd forgotten it was the light in this window that we saw from the outside,” Dr. Ringwood interrupted. “Go on.”
“Then, very quietly, by shifting the table on the landing under the electric light, X removed the bulb that lighted the stair. One can reach it by standing on that table. Then X shifted the table back to its place. There were no finger-prints on the bulb—ergo, X must have been wearing gloves, as I told you.”
“You seem to have got a lot of details,” the doctor admitted. “But why all this manœuvring?”
“You'll see immediately. I think I said already that whoever did the business was a very cool and competent person. When all was ready, X attracted the maid's attention in some way. She came to the foot of the stairs, suspecting nothing, but probably wondering what X was doing, wandering about the house. It's quite likely that X made the sick girl upstairs the pretext for calling and wandering out of bounds. Anyhow, the maid came to the foot of the stairs and moved the switch of the landing light. Nothing happened, of course, since the bulb had been removed. She tried the switch backwards and forwards once or twice most likely, and then she would conclude that the lamp was broken or the fuse gone. Probably she saw the reflection of the light from the room-door. In any case, she came quite unsuspiciously up the stair.”