Antony laughed and denied it cheerfully.

“Then how do you know?”

“You’re the perfect Watson, Bill. You take to it quite naturally. Properly speaking, I oughtn’t to explain till the last chapter, but I always think that that’s so unfair. So here goes. Of course, I don’t really know that he’s got it, but I do know that he had it. I know that when I came on him this afternoon, he had just locked the door and put the key in his pocket.”

“You mean you saw him at the time, but that you’ve only just remembered it⁠—reconstructed it⁠—in the way you were explaining just now?”

“No. I didn’t see him. But I did see something. I saw the key of the billiard-room.”

“Where?”

“Outside the billiard-room door.”