Downstairs in the lounge, by the third pillar from the left, there sits an old lady with a sweet, placid, spinsterish face and a mind that has plumbed the depths of human iniquity and taken it all as in the day's work....where crime is concerned, she's the goods.

It is ridiculous to set a detective story in New York City. New York City is itself a detective story.

Nobody knows what another person is thinking. They may imagine they do, but they are nearly always wrong.

Ah, but life is like that! It does not permit you to arrange and order it as you will. It will not permit you to escape emotion, to live by the intellect and by reason! You cannot say, 'I will feel so much and no more.' Life, Mr. Welman, whatever else it is, is not reasonable. [Hercule Poirot]

But I know human nature, my friend, and I tell you that, suddenly confronted with the possibility of being tried for murder, the most innocent person will lose his head and do the most absurd things.

Nothing, I believe, is so full of life under the microscope as a drop of water from a stagnant pool.

Sometimes I feel sure he is as mad as a hatter and then, just as he is at his maddest, I find there is a method in his madness.