You’re suggesting the mysterious X. Where do we look for…

““You’re suggesting the mysterious X. Where do we look for him?’ Poirot said: ‘Obviously in a close circle. There were five people, were there not, whocould have been concerned?’ ‘Five? Let me see. There was the old duffer who messed about with his herb brewing. A dangerous hobby-but an amiable creature. Vague sort of person. Don’t see him as X. There was the girl-she might have polished off Caroline, but certainly not Amyas. Then there was the stockbroker-Crale’s best friend. That’s popular in detective stories, but I don’t believe in it in real life. There’s no one else-oh yes, the kid sister, but one doesn’t seriously consider her. That’s four.’ Hercule Poirot said: ‘You forget the governess.’ ‘Yes, that’s true. Wretched people, governesses, one never does remember them. I do recall her dimly though. Middle-aged, plain, competent. I suppose a psychologist would say that she had a guilty passion for Crale and therefore killed him. The repressed spinster! It’s no good-I just don’t believe it. As far as my dim remembrance goes she wasn’t the neurotic type.’ ‘It is a long time ago.’ ‘Fifteen or sixteen years, I suppose. Yes, quite that. You can’t expect my memories of the case to be very acute.””

— Agatha Christie