s brown suit was known to the police. Couldn't
Cayley have brought him another one in the passage, to escape in, and
then have had the brown one on his hands? And thought it safest to hide
it in the pond?"

"Yes," said Anthony thoughtfully. Then: "Go on."

Bill went on eagerly:

"It all seems to fit in, you know. I mean even with your first
theory--that Mark killed him accidentally and then came to Cayley for
help. Of course, if Cayley had played fair, he'd have told Mark that he
had nothing to be afraid of. But he isn't playing fair; he wants to get
Mark out of the way because of the girl. Well, this is his chance. He
makes Mark as frightened as possible, and tells him that his only hope
is to run away. Well, naturally, he does all he can to get him well
away, because if Mark is caught, the whole story of Cayley's treachery
comes out."

"Yes. But isn't it overdoing it rather to make him change his
underclothes and everything? It wastes a good deal of time, you know."

Bill was pulled up short, and said, "Oh!" in great disappointment.

"No, it's not as bad as that, Bill," said Antony with a smile. "I
daresay the underclothes could be explained. But here's the difficulty.
Why did Mark need to change from brown to blue, or whatever it was, when
Cayley was the only person who saw him in brown?"

"The police description of him says that he is in a brown suit."

"Yes, because Cayley told the police. You see, even if Mark had had
lunch in his brown suit, and the servants had noticed it, Cayley could
always have pretended that he had changed into blue after lunch, because
only Cayley saw him afterwards. So if Cayley had told the Inspector that
he was wearing blue, Mark could have escaped quite comfortably in his
brown, without needing to change at all."

"But that's just what he did do," cried Bill triumphantly. "What fools
we are!"

Antony looked at him in surprise, and then shook his head.

"Yes, yes!" insisted Bill. "Of course! Don't you see? Mark did change
after lunch, and, to give him more of a chance of getting away, Cayley
lied and said that he was wearing the brown suit in which the servants
had seen him. Well, then he was afraid that the police might examine
Mark's clothes and find the brown suit still there, so he hid it, and
then dropped it in the pond afterwards."

He turned eagerly to his friend, but Antony said nothing. Bill began to
speak again, and was promptly waved into silence.

"Don't say a