The impossible could not have happened, therefore the impossible must be possible in spite of appearances.

One knows so little. When one knows more it is too late.

Curious things, habits. People themselves never knew they had them. [Witness for the Prosecution, also published in The Hound of Death and Other Stories.]

Your not reliable. You wouldn't be at all a comfortable sort of person to live with.

There hung about her the restrained energy of a whiplash.

the detective's highest talent lay in the gentle art of seeking favours under the guise of conferring them!

Any woman can fool a man if she wants to and if he's in love with her.