come out sooner or later. He had strolled along the front and round
Brunswick Square. Marley shrugged his shoulders.

"Well, it's a bit of a puzzle to me," he admitted. "You go out for a
midnight walk--a thing you have never done before--and when you come back
you find somebody has got into your house by means of a stolen latch-key
and murdered somebody else in your conservatory. According to that, two
people must have entered the house."

"That's logic," David admitted. "There can be no murder without the slain
_and_ the slayer. My impression is that somebody who knows the ways of
the house watched me depart. Then he lured his victim in here under
pretence that it was his own house--he had the purloined latch-key--and
murdered him. Audacious, but a far safer way than doing it out of doors."

But Marley's imagination refused to go so far. The theory was plausible
enough, he pointed out respectfully, if the assassin had been assured
that these midnight rambles were a matter of custom. The point was a
shrewd one, and Steel had to admit it. He almost wished now that he had
suggested that he often took these midnight rambles. He regretted the
fiction still more when Marley asked if he had had some appointment
elsewhere to-night.

"No," David said, promptly, "I hadn't."

He prevaricated without hesitation. His adventure in Brunswick Square
could not possibly have anything to do with the tragedy, and nothing
would be gained by betraying that trust.

"I'll run round to the hospital and come and see you again in the