Progress in the murder investigation is slow until the Reverend's wife, Mrs. Dane Calthrop, invites Miss Marple to investigate. Jerry conveys many facts about the case to her from his observations, and tells her some of his ideas on why Agnes was killed. Meanwhile, Elsie Holland, the governess for the Symmington boys, receives an anonymous letter. The police observe Aimée Griffith, sister of the local doctor Owen Griffith, typing the address on the same typewriter used for all the previous letters, and arrest her for writing the letter.

Heading to London to see his doctor, Jerry impulsively takes Megan along with him and takes her to Joanna's dressmaker for a complete makeover. He realises he has fallen in love with Megan. When they return to Lymstock, Jerry asks Megan to marry him; she turns him down. He asks Mr Symmington for his permission to pursue Megan. Miss Marple advises Jerry to leave Megan alone for a day, as she has a task for her.

Megan blackmails her stepfather later that evening, implying that she has proof that he killed Mrs. Symmington. Mr. Symmington coolly pays her an initial instalment of money while not admitting his guilt. Later in the night, after giving Megan a sleeping drug, he attempts to murder her by putting her head in the gas oven. Jerry and the police are lying in wait for him. Jerry rescues Megan, and Symmington confesses. The police arrest him for murdering his wife and Agnes.