“The sort which old gentlemen have to keep out draughts?”

“Yes. Just at first they hardly move at all, and then very, very slowly they swing to⁠—well, that was the way the shadow moved, and subconsciously I must have associated it with the movement of that sort of door. By Jove!” He got up, and dusted his knees. “Now, Bill, just to make sure, go in and close the door like that. As an afterthought, you know; and very quietly, so that I don’t hear the click of it.”

Bill did as he was told, and then put his head out eagerly to hear what had happened.

“That was it,” said Antony, with absolute conviction. “That was just what I saw yesterday.” He came out of the office, and joined Bill in the little room.