Hastings rushes to the shed and finds Giraud already conducting a meticulous examination. The victim, a man of about 50, lies on his back with the distinctive dagger hilt visible above his heart. Giraud immediately establishes that the man wasn’t killed there because the tidy arrangement of the corpse shows he was moved after death. The body was dragged by two people, one of whom Giraud identifies as a woman from a partial shoe print. He also produces a long black hair wound around the dagger handle, which is similar to one Poirot previously retrieved from the library armchair. Giraud notes that the victim’s hands are rough with broken nails, yet his clothing is expensive and well-tailored, suggesting a deliberate disguise of his social standing. The dagger bears no fingerprints, as in the first murder.

Mrs. Renauld, Jack, and Madame Daubreuil are each brought in to view the body, and all deny recognizing the man. Giraud lets Daubreuil go but places her under surveillance. When the examining magistrate and Dr. Durand arrive, Giraud speculates that the killing followed shortly after the dagger’s theft the previous morning. Dr. Durand contradicts him, saying the man has been dead at least 48 hours.

The revelation that the victim died two days before the dagger was stolen leaves everyone baffled. A telegram arrives from Poirot announcing his return on the 12:28 train. While waiting at the station, Hastings questions the chief porter about departures on the night of the murder. On impulse, he asks about Jack and learns that Jack arrived in Merlinville on the 11:40 train, explaining both Marthe’s anxiety and Jack’s silence on the matter.

Poirot arrives in high spirits, declaring his Paris trip a success. When told of the second murder, he’s briefly shaken but composes himself and accurately predicts that the body of a middle-aged man who’d been stabbed was found in the nearby shed and had been dead at least 48 hours. Walking to the villa, Poirot raises the possibility of two identical daggers, noting the weapon was a custom-made war souvenir ordered for Jack and that a duplicate is plausible.

At the shed, Poirot examines the body. He notices foam on the dead man’s lips and the lack of bloodstains around the wound, signs he was stabbed after his death to make it appear that he’d been murdered. Giraud agrees. Poirot declares the actual cause of death was an epileptic fit, and Dr. Durand confirms this on re-examination. Back at the hotel, Poirot produces a faded newspaper clipping bearing a woman’s photograph, which he acquired during his trip to Paris. Hastings recognizes a younger Madame Daubreuil. Back then, she was known as Madame Beroldy, the central figure in a famous murder case.

Roughly 20 years earlier, Arnold Beroldy, an unremarkable junior partner in a firm of wine merchants, settled in Paris with his wife, Jeanne, and their infant daughter. Jeanne was striking and socially magnetic, cultivating rumors of noble birth. She drew admirers, including a young lawyer named Georges Conneau and a wealthy American named Hiram P. Trapp. She encouraged Conneau discreetly while hinting to friends that her husband was entangled in dangerous political intrigue involving secret papers of great significance.

One November morning, the Beroldys’ cleaning woman found the apartment door open, Jeanne bound and gagged on the floor, and Arnold stabbed through the heart. Jeanne claimed two masked Russians had demanded the secret papers and killed her husband when he refused. The story gripped the public, but the masked men were never found, and Jeanne was eventually arrested and charged with the murder herself.

At trial, her invented history about her aristocratic birth was demolished. The prosecution argued her true motive was to free herself from a dull husband to marry Trapp, who admitted he would have proposed had she been a widow. Conneau vanished but, after learning of Jeanne’s interest in Trapp, he posted a letter confessing he killed Arnold at Jeanne’s instigation. Jeanne promptly abandoned the story of Russian intruders and claimed Conneau had acted alone and threatened her into silence. Her closing address to the jury skillfully emphasized her grief and concern for her daughter, and she was acquitted. Conneau was never apprehended, and Jeanne disappeared with her daughter to begin a new life.

The narrative returns to the present. Hastings immediately concludes that Madame Daubreuil, the former Madame Beroldy, murdered Renauld, citing the parallels between the two cases. Poirot challenges him to supply a motive and points out that, as Renauld’s mistress or his potential blackmailer, Daubreuil stood only to lose by his death. He also notes that the grave was likely dug by a man and that her entire history reveals a calculating rather than impulsive nature. More pointedly, he observes that the story of masked intruders with a secret was told this time by Mrs. Renauld, not Daubreuil, and he doesn’t believe the two women are conspiring together.

Poirot declares that he’s identified one murderer and solved what Renauld originally hired him to find, but he states that “for two crimes it is essential to have two bodies” (141). Before Hastings can press further, Jack arrives, summoned by a note from Poirot. Poirot fabricates a story about the foreign suspects leaving a suitcase behind and asks Jack to inquire at the nearby station of Abbalac. Before Jack leaves, Poirot confronts him about his unannounced presence in Merlinville on the night of his father’s murder. Jack claims he came to see Marthe, missed the last train, walked 15 kilometers to Saint-Beauvais, and hired a car back to Cherbourg. Once Jack departs, Poirot tells Hastings that the errand was a fabrication designed to keep Jack occupied while they search his room.

At the Villa Geneviève, Poirot tells Marthe that Giraud suspects Jack of the murder. Shaken but resolute, she admits that Jack told her that he came to Merlinville on the night of the murder, but she insists on his innocence. She also discloses something she had withheld: On the morning before the murder, she saw Renauld arguing through the garden hedge with an unhoused man in ragged clothes who was demanding money. She is now nearly certain the man and the body in the shed are the same person, despite the change of clothing.

After Marthe is called away, Poirot notes that her phrasing when asked about Jack’s presence on the night of the murder shows she didn’t actually see Jack, contradicting Jack’s claim that he visited her. Poirot outlines the theory Giraud is likely building: Jack killed his father for the inheritance, used the unhoused man as an accomplice, and then silenced him. Poirot says Giraud has reinterpreted the strand of hair found on the dagger as the long hair of a fashionable young man, but Poirot himself knows it belongs to a woman, and he claims he knows which woman.

Poirot and Hastings search Jack’s room and are nearly finished when Hastings spots a car pulling up carrying Giraud, Jack, and two officers. Poirot hurriedly seizes a small photograph from a drawer and pockets it before going downstairs. In the hall, Giraud announces he caught Jack attempting to flee and has arrested him for the murder of his father. Confronted by Poirot, Jack says nothing in his own defense.