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

Do you believe in the value of truth, my dear, or don’t you?” “Of course I believe in the truth,” said Rhoda, staring. “Yes, you say that, but perhaps you haven’t thought about it. The truth hurts sometimes – and destroys one’s illusions.” “I’d rather have it all the same.” said Rhoda. “So would I. But I don’t know that we’re wise.” Mrs. Oliver; Rhoda Dawes

Many years ago, when I was once saying sadly to Max it was a pity I couldn't have taken up archaeology when I was a girl, so as to be more knowledgeable on the subject, he said, 'Don't you realize that at this moment you know more about prehistoric pottery than any woman in England?'

As you yourself have said, what other explanation can there be?' Poirot stared straight ahead of him. 'That is what I ask myself,' he said. 'That is what I never cease to ask myself.

I have always been so sure - too sure... But now I am very humble and I say like a little child: "I do not know..."

What's wrong with my proposition?" Poirot rose. "If you will forgive me for being personal-I do not like your face, M. Ratchett.

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