At the end of a quiet summer, an ailing, sharp-tongued widow named Lady Tressilian gathers a small circle of guests at Gull's Point, her house on the cliffs above an English seaside town. Among them is the tennis champion Nevile Strange, a former ward of her late husband, who arrives with an arrangement that scandalises his hostess: he brings both his composed first wife and his volatile new one under the same roof. Old loyalties, jealousies, and resentments simmer through tense dinners and strained walks along the shore, and several of the visitors carry private griefs that have nothing to do with tennis. When violence finally erupts in the house, Superintendent Battle, holidaying nearby with his nephew Inspector Leach, is drawn into the case. The investigation unfolds around an unusual idea, voiced early on by an elderly observer: that a murder is not the start of a story but its end point, the moment toward which a long chain of small decisions and old wounds has been quietly moving. Battle works backward through the household's tangled relationships, testing alibis, weighing motives, and separating accident from design as evidence accumulates and suspicion shifts. Tightly plotted and built on character rather than spectacle, the novel studies how grievance hardens into intent and how the apparently incidental moments preceding a crime turn out to matter most. The result is a closed-circle puzzle in which the convergence itself, not just its solution, is the heart of the design.