mes straight in through the windows.
Now, I'm going to shut the door. Look! D'you see how the shadow moves
across? That's what I saw the shadow moving across as the door shut
behind him. Bill, go in and shut the door behind you quite naturally.
Quick!"

Bill went out and Antony knelt, watching eagerly.

"I thought so!" he cried. "I knew it couldn't have been that."

"What happened?" said Bill, coming back.

"Just what you would expect. The sunlight came, and the shadow moved
back again all in one movement."

"And what happened yesterday?"

"The sunlight stayed there; and then the shadow came very slowly back,
and there was no noise of the door being shut."

Bill looked at him with startled eyes.

"By Jove! You mean that Cayley closed the door afterwards as an
afterthought and very quietly, so that you couldn't hear?"

Antony nodded.

"Yes. That explains why I was surprised afterwards when I went into
the room to find the door open behind me. You know how those doors with
springs on them close?"

"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.

"And now," he said, "let's try and find out what it was that Mr. Cayley
was doing in here, and why he had to be so very careful that his friend
Mr. Gillingham didn't overhear him."

CHAPTER XIII. The Open Window

Anthony's first thought was that Cayley had hidden something; something,
perhaps, which he had found by the body, and but that was absurd. In the
time at his disposal, he could have done no more than put it away in a
drawer, where it would be much more open to discovery by Antony than if
he had kept it in his pocket. In any case he would have removed it by
this time, and hidden it in some more secret place. Besides, why in this
case bother about shutting the door?

Bill pulled open a drawer