almost any house, you'll find the keys all ready, so that you can lock yourself in at a moment's notice. But downstairs people don't lock themselves in. It's really never done at all. Bill, for instance, has never locked himself into the dining-room in order to be alone with the sherry. On the other hand, all women, and particularly servants, have a horror of burglars. And if a burglar gets in by the window, they like to limit his activities to that particular room. So they keep the keys on the outside of the doors, and lock the doors when they go to bed." He knocked the ashes out of his pipe, and added, "At least, my mother always used to."
"You mean," said Bill excitedly, "that the key was on the outside of the door when Mark went into the room?"
"Well, I was just wondering."
"Have you noticed the other rooms—the billiard-room, and library, and so on?" said Cayley.
"I've only just thought about it while I've been sitting out here. You live here—haven't you ever noticed them?"
Cayley sat considering, with his head on one side.
"It seems rather absurd, you know, but I can't say that I have." He turned to Bill. "Have you?"
"Good Lord, no. I should never worry about a thing like that."
"I'm sure you wouldn't," laughed Antony. "Well, we can have a look when we go in. If the other
