General Ravenscroft and his wife, Margaret, are found dead at their estate in the English countryside. They were discovered together, both shot in the head, but there are few clues to suggest a motive for the crime. Despite extensive investigations at the time, the case remains unsolved, and the deaths are presumed to have been part of a tragic, mysterious double murder.

Years later, Hercule Poirot and Captain Hastings are discussing the case when a mutual acquaintance, Dame Daphne, urges Poirot to look into the Ravenscroft murders once again. Dame Daphne has a personal interest in the case, as she was close to the Ravenscroft family and has heard conflicting reports about what really happened that night. Her desire for closure leads Poirot to investigate further.