The Full Story

The story begins with Hercule Poirot receiving an urgent letter from a wealthy Frenchman, Paul Renauld, living in the seaside resort of Merlinville-sur-Mer, France. Renauld claims his life is in danger and desperately requests Poirot's assistance, stating he cannot trust the local police. Poirot, accompanied by Captain Hastings, immediately travels to France.

However, upon their arrival, they are met with grim news: Paul Renauld has been found murdered. His body is discovered stabbed in the back with a letter opener, lying face down in a freshly dug grave on his newly constructed golf course. The local police, led by the arrogant and dismissive Inspector Giraud, are already on the scene. Giraud, a proponent of "scientific" detection, quickly dismisses Poirot's "psychological" methods, leading to a rivalry between the two detectives.

Renauld's wife, Eloise Renauld, claims that two masked men broke into their villa in the early hours of the morning, tied her up, and abducted her husband. She insists she heard them threaten him before they took him away. However, Poirot immediately suspects her story.

As Poirot investigates, a baffling array of clues and suspects emerge:

• Paul Renauld's past: It's revealed that Renauld, originally Georges Conneau, had a criminal past in France. Years ago, he and his lover, Madame Beroldy, had conspired to murder Madame Beroldy's husband. Conneau escaped justice and fled to South America, where he amassed his fortune and married Eloise.
• A second body: To further complicate matters, another body is found, stabbed identically. This second victim is initially identified as a tramp, but Poirot's keen eye notes inconsistencies. It is later revealed that the tramp died of an epileptic seizure before Renauld's murder and was merely used to stage a complex deception.
• Madame Daubreuil: Renauld's neighbor, a mysterious and elegant woman named Madame Daubreuil, is recognized by Poirot as the former Madame Beroldy, Renauld's accomplice from his past. She had been blackmailing Renauld, and her daughter, Marthe Daubreuil, is romantically involved with Renauld's son, Jack.
• Jack Renauld: Paul Renauld's son, Jack, had a contentious relationship with his father and is initially the prime suspect for Inspector Giraud, especially after it's discovered Paul had disinherited him just two weeks before his death.
• "Cinderella" and Bella Duveen: Captain Hastings becomes infatuated with a young stage performer named Bella Duveen, whom he nicknames "Cinderella." She appears to have some connection to the case, and her sister, Dulcie Duveen, is also involved in the convoluted events.

Poirot meticulously examines every detail, from the position of a hearth rug to the specific type of cigarette smoked. He realizes that Renauld had concocted an elaborate plan to fake his own death to escape Madame Daubreuil's blackmail. He planned to use the tramp's body to stage the murder, bury it on the golf course, and then disappear. However, his plan was intercepted.

The truth, as uncovered by Poirot, is incredibly complex: Paul Renauld was indeed trying to fake his death. He had dug the grave and was preparing to dispose of the tramp's body when he was murdered. The real killer is Marthe Daubreuil, the daughter of Madame Daubreuil. Marthe, driven by greed and a desire to secure her future with Jack, knew of Renauld's plan and saw an opportunity. She followed Renauld to the golf course and stabbed him after he had already dug the grave for the tramp's body, making it appear as if he had been killed by an unknown assailant and left in a prepared grave.

Marthe's motive was to ensure that Jack would inherit his father's fortune upon his mother's death, as she believed this would lead to her own financial security. She also tried to implicate others to throw off the scent.

In the end, Poirot exposes Marthe's cunning scheme, much to the chagrin of Inspector Giraud, who had consistently underestimated the Belgian detective. The novel also features a romantic subplot as Captain Hastings finds love with Bella Duveen.