James Bentley is tried for the murder of Abigail McGinty, the charwoman of Broadhinny who also took in Bentley as her lodger. The evidence is overwhelming, and soon after he is sentenced to hang. Superintendent Spence is not convinced of the man's guilt, and so he visits Poirot, asking him to look into the case. Poirot then heads off to the village, where he becomes the paying guest of Maureen and Major Johnnie Summerhayes. Ariadne Oliver, Poirot's novelist friend, has also come to Broadhinny to collaborate on a stage adaptation of one of her novels with dramatist Robin Upward. With the clue of a bottle of ink purchased by the dead woman shortly before her death, Poirot searches Mrs. McGinty's belongings and finds an edition of The Sunday Comet newspaper, where an article concerning two women connected with famous murders has been cut out. With the story are two photographs of the women. Poirot discovers that Mrs. McGinty had seen one of the photographs before, and knew to whom it belonged to. But which woman was this case connected with? Are any of the people living in Broadhinny related to these women, as one of their children? Or perhaps one of them is one of the actual women? The puzzle pieces begin to fit in, especially after Poirot is shoved into the path of an oncoming train by an unknown entity. But will the murderer strike again?
