James Bentley is arrested for the murder of old Mrs McGinty. It looks like an open and shut case, but Superintendent Spence is not convinced. He turns to Poirot for help, and together with Poirot's writer friend Ariadne Oliver they set out to find the real killer.

On holiday in Jerusalem, Poirot hears about an archaeological expedition to Syria led by the eccentric Lord Boynton and his son Leonard, who believe they are on the track of the head of St John the Baptist. Drawn to visit the dig, Poirot meets Boynton's dominating, fabulously rich, American-born second wife. However, events are overtaken by the discovery of Lady Boynton's dead body and revelations about her fortune.

Four clocks surround an unidentified corpse in a blind woman's house, and a young typist is summoned to the crime scene. However, Poirot is convinced that the complicated setup is merely hiding a simpler solution.