Never do anything yourself that others can do for you.

I am not one to rely upon the expert procedure. It is the psychology I seek, not the fingerprint or the cigarette ash.

... there are many to whom money has no personal appeal, but who can be tempted by the power it confers.

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.

Words are such uncertain things, they so often sound well but mean the opposite of what one thinks they do.

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