"So you mentioned," Peter said slowly. "But if everybody who locked a door—"
"I can only think of two kinds of people who'd lock their bedroom doors when they were staying in a private house," said the Saint. "Frightened virgins and — frightened men."
"Maybe he was expecting a call from Lady Valerie," suggested Patricia half heartedly.
"Maybe he was," agreed the Saint patiently. "But if that made him lock his door, he must have been a very undiscriminating young man. And in any case, that's only half of it. He not only locked his door, but he took the key out of the lock. Now, even assuming that anyone might lock a door, there's only one reason for taking the key out of the lock. And that's when you realize that an expert might be able to turn the key from the outside — in other words, when you're really thinking hard along the lines of a pretty determined attempt to get at you."
"He might have been tight when he went to bed," Peter pointed out. "That would account for almost any weird thing he did. And besides that, it might account for him not hearing the fire alarm."
"It might," said the Saint bluntly. "But while you're at it, why don't you think of the other possibility? Suppose he didn't lock the door at all. Suppose somebody else did?"
They were silent again.
"Go on," said Patricia.
Simon looked at her.
"Two: during all the time we were there, did you see any signs of a servant?"