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.
If you confront anyone who has lied with the truth, he will usually admit it - often out of sheer surprise. It is only necessary to guess right to produce your effect.
“My dear Monsieur Poirot—how can I put it? It’s like the moon when the sun comes out. You don’t know it’s there anymore. When once I’d met Linnet—Jackie didn’t exist.”