The story takes place in the English village of Woodleigh Common, where a Halloween party is being held for local children. During the event, a boastful 13-year-old girl named Joyce Reynolds claims she once witnessed a murder, though she didn’t realize it at the time. Her statement is dismissed as tention-seeking.

However, later that night, Joyce is found drowned in an apple-bobbing tub, shocking the community. Ariadne Oliver, the famous crime novelist and friend of Poirot, was at the party and urges him to investigate, convinced that Joyce’s claim was true—and that someone killed her to keep a dark secret hidden.