When a woman is discovered dead in a locked room with a pistol in her hand, Hercule Poirot must determine if the scene is a tragic suicide or a calculated homicide. Poirot faces the challenge of a seemingly airtight case where the physical evidence—specifically the angle of the gunshot wound—contradicts the initial police conclusion. He must navigate the social constraints of 1930s London while relying on his meticulous observation of human behavior to expose the truth. The narrative follows a classic investigative framework, focusing on the logical deconstruction of a crime scene.

This work is widely regarded as a quintessential example of the classic British detective novella, showcasing the author's ability to construct a complex puzzle within a limited page count. Readers often highlight the clever use of physical evidence, such as the handedness of the victim, as a hallmark of the genre's golden age. The story remains a staple for fans of the Poirot series, frequently praised for its tight plotting and the effective dynamic between the detective and his associates. Its enduring popularity is evidenced by its successful adaptation for television, which introduced the narrative to a new generation of mystery enthusiasts.