Captain Hastings, wounded at the Front in World War 1, is recuperating at Styles Court in Essex. The house belongs to the Inglethorpe family, friends from his childhood. When Emily Inglethorpe is found poisoned, it is fortunate for Hastings that he bumps into his old friend Hercule Poirot, who can help to solve this horrible murder. When the evidence seems to point to one particular family member it is up to Poirot, through his methodical investigation, to prove the real murderer is someone else entirely.