Sir Clinton paused, as though to allow the doctor to raise objections; but none came, so he continued:
“Meanwhile X had taken up a position opposite the door of the room, at the foot of the second flight of stairs. If you remember, a person crouching there in semi-darkness would be concealed from anyone mounting the first flight. The tourniquet was ready, of course.”
Dr. Ringwood shuddered slightly. Apparently he found Sir Clinton's picture a vivid one, in spite of the casual tone in which it had been drawn.
“The girl came up, quite unsuspicious,” Sir Clinton continued. “She knew X; it wasn't a question of a street-loafer or anything of that sort. An attack would be the last thing to cross her mind. And then, in an instant, the attack fell. Probably she turned to go into the lighted room, thinking that X was there; and then the noose would be round her neck, a knee would be in her back and . . .”
With a grim movement, Sir Clinton completed his narrative of the murder more effectively than words could have done.
“That left X a clear field. The girl upstairs was light-headed and couldn't serve as a witness. X daren't go near her for fear of catching scarlatina—and that would have been a fatal business, for naturally we shall keep our eye on all fresh scarlet cases for the next week or so. It's on the cards that her scarlatina has saved her life.”
Dr. Ringwood's face showed his appreciation of this point.
“And then?” he pressed Sir Clinton.
“The rest's obvious. X came in here, hunting for something which we haven't identified. Whatever it was, it was in this drawer and X knew where it was. Nothing else has been disturbed except slightly—possibly in a hunt for the key of the drawer in case it had been left lying around loose. Not finding the key, X broke open the drawer and then we evidently arrived. That must have been a nasty moment up here. I don't envy friend X's sensations when we rang the front door bell. But a cool head pulls one through difficulties of that sort. While we were standing unsuspiciously on the front door steps, X slipped down stairs, out of the back door, and into the safety of the fog-screen.”
The Chief Constable rose to his feet as he concluded.