The red thumb-mark filled my field of vision to the exclusion of all else.

To me, as to everyone else but Thorndyke, this fact was final and pointed to a conclusion that was unanswerable.

But as I turned the story of the crime over and over, there came to me presently an idea that set in motion a new and very startling train of thought.
Could Mr.Hornby himself be the thief?
His failure appeared sudden to the outside world, but he must have seen difficulties coming.

There, indeed, was the thumb-mark on the leaf which he had torn from his pocket-block.

Yes! but who had seen him tear it off?
No one.