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In “Curtain”, Hercule Poirot’s last case, he faces a very unusual murderer, who kills only for pleasure, and never personally pulls the proverbial trigger. Instead, he finds people in difficult situations: a young woman forced to give up her life to care for an invalid mother, a protective father seeing his naive daughter falling for a lothario, a henpecked husband continually tormented by an overbearing wife. He then manipulates the situation to make it go from miserable to intolerable. He never cousels murder, but he needles, and goads, and manufactures flash point incidents with a deft hand. Of course, he doesn’t have a 100% “success” rate, but he is responsible for some half dozen murders by Poirot’s count.
I won’t tell you how Poirot deals with him, but how would we deal with it today in real life? Take it as read (ha) that this guy can persuade ordinary people to commit murder, how do we stop him. Can he be arrested? He never tells anyone to do violence. He just makes it inevitable that they will. Could he be publicly exposed so people would have their guards up? Poirot’s solution, if you know it, seems a bit off the ideal, but I can’t really come up with anything better.