Hercule Poirot arrives in France to assist a client, only to discover that the man has already been murdered. The detective must navigate a complex web of deception involving the victim's family, a mysterious woman, and a rival French investigator. As a second body appears with identical wounds, Poirot faces the challenge of reconciling conflicting testimonies and hidden motives. The narrative unfolds through a third-person perspective, emphasizing the methodical gathering of clues and the psychological profiling of suspects.

Readers often highlight this novel as a pivotal moment in the development of Hercule Poirot's character and his professional rivalry with the French police. The intricate plotting is frequently cited as a hallmark of Christie's ability to construct layered puzzles that challenge the reader's perception of truth. Critics have noted that the setting of northern France provides a distinct atmosphere that separates this case from the more domestic English mysteries. The resolution is widely regarded as a clever subversion of expectations that rewards those who pay close attention to the small details provided throughout the investigation.