“I could very easily give you half a dozen,” said Holmes. “Here for example, is a very possible and even probable one. I make you a free present of it. The older man is showing documents which are of evident value. A passing tramp sees them through the window, the blind of which is only half down. Exit the solicitor. Enter the tramp! He seizes a stick, which he observes there, kills Oldacre, and departs after burning the body.”

“Why should the tramp burn the body?”

“For the matter of that, why should McFarlane?”

“To hide some evidence.”

“Possibly the tramp wanted to hide that any murder at all had been committed.”

“And why did the tramp take nothing?”

“Because they were papers that he could not negotiate.”

Lestrade shook his head, though it seemed to me that his manner was less absolutely assured than before.