Quick recap
Widowed Hastings returns to Styles, now a guesthouse, at Poirot's request. The detective is old and in a wheelchair, but his mind is as sharp as ever. He warns that among the guests is a killer he calls X: someone tied to five old deaths without ever laying a hand on anyone. Hastings's daughter Judith is there too. In the end, in a letter left for Hastings, Poirot reveals that X is Stephen Norton, a man who drove others to kill. Unable to prove it in court, Poirot kills Norton himself. Then he stops taking his heart medicine and dies. Hastings reads the letter four months later.
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