"It's pretty maddening to think that an important secret may lie here on this slip of paper, and that it is beyond human power to penetrate it." Sherlock Holmes had pushed away his untasted breakfast and lit the unsavoury pipe which was the companion of his deepest meditations.

"I wonder!" said he, leaning back and staring at the ceiling.

"Perhaps there are points which have escaped your Machiavellian intellect.

Let us consider the problem in the light of pure reason.

This man's reference is to a book.