The morning routine at Gossington Hall shatters when a maid discovers the body of an unknown young woman sprawled on the library floor. The dead girl is a platinum blonde in a cheap evening dress, a stranger to the respectable household of Colonel Arthur Bantry and his wife Dolly. As gossip threatens to brand the Colonel a suspect in his own home, Dolly turns to her shrewd friend from St. Mary Mead, an elderly spinster who understands village human nature better than anyone. The victim is soon identified as a dancer from a nearby seaside resort hotel, a young woman who had drawn the devotion of a wealthy, grieving invalid and the resentment of his relations. The local police pursue alibis and motives through the hotel's bright world of bridge tables and exhibition dances, while the spinster watches, listens, and draws her own quiet parallels to people she has known. A second discovery widens the case and confuses the timeline, forcing every theory to be reconsidered. Working alongside an old acquaintance from Scotland Yard and a methodical superintendent, she sifts the small inconsistencies others overlook. The investigation moves between the orthodox calm of an English country house and the restless energy of resort society, where appearances rarely hold. What seems an impossible intrusion proves to be a carefully arranged crime, and only patient attention to character reveals the design behind it.