The next morning, the maid Léonie tells Poirot that Mrs. Renauld is devastated and barely eating. She also recalls that shortly before Jack left for Paris, he and his father had a furious argument.

While Poirot settles in the salon, Hastings heads outside and pushes through dense shrubbery onto the golf course, where he collides with the young woman he met on the train. Both are astonished. “Cinderella” says she’s staying in Merlinville but offers no further explanation. When Hastings mentions the Villa Geneviève murder, she begs to be shown the scene, hinting she might sell an inside account to a newspaper.

Hastings reluctantly agrees, obtains the shed key, and guides her to the grave site and the shed. Inside, he shows her the body and points out the murder weapon sitting in a glass jar. The girl collapses. Hastings rushes to the house for water and brandy, revives her, and escorts her out. She pulls the shed door shut behind them.

Hastings walks her to the edge of town, where they part. She tells him she’s staying at the Hôtel du Phare and invites him to visit the next day. On his way back, he realizes he forgot to relock the shed during the confusion and corrects the oversight. He also realizes that, although she gave him her address, he still doesn’t know her real name.

Back in the salon, Hautet questions Auguste about his gardening gloves and the spade. Hastings asks Auguste about his boots, keeping Poirot’s interest in the footprints in mind, but learns nothing useful.

Giraud then appears at the open window and notes that holding an interrogation beside it lets anyone outside overhear. He produces a cigarette stub and an unlit match, both of South American origin, which he sees as a clue to the killers’ provenance. Poirot asks dryly where the match that actually lit the cigarette is, and Giraud has no answer. Hautet briefs Giraud on the mysterious late-night visitor, the letter from “Bella,” and the check to Duveen. Giraud theorizes that an accomplice with a key admitted the killers, and he suggests Jack or Madame Daubreuil may have done so. Poirot challenges him to explain why the killers would leave the front door open when departing. Giraud dismisses it as an oversight, but Poirot insists the open door was necessary and that any theory ignoring it will fail.

Poirot adds that a nearly identical crime has been committed before and that criminals tend to repeat their methods. He then raises two further details: Mrs. Renauld’s wristwatch was two hours fast, and there are the footprints in the flower bed. When Giraud looks out the window at the flower bed beneath it, Poirot informs him there are no footprints there. Giraud’s fury is interrupted by the announcement that Gabriel Stonor, Renauld’s secretary, has arrived from England.

Stonor confirms that Renauld was clearly unsettled in the weeks before his death, though he never explained why. Renauld was similarly guarded about his life before South America. Stonor knows he was French-Canadian by birth but never heard him discuss his early years. Stonor doesn’t recognize the names “Bella” or “Duveen,” though the latter strikes him as vaguely familiar.

When Hautet raises the theory of a romantic involvement with Madame Daubreuil, Stonor rejects it, insisting the Renaulds were a devoted couple. He confirms that he personally transmitted 200,000 francs to Daubreuil in cash at Renauld’s request, but he declares the payments were blackmail and argues that Daubreuil must have known something damaging about Renauld’s past.

Hautet reveals that Renauld drew up a new will less than a fortnight before his death, leaving his entire fortune to his wife and omitting his son entirely. Stonor is surprised but reads it as further evidence of the couple’s devotion. Poirot inquires whether the chauffeur, Masters, has South American connections. Stonor confirms he has none and vouches for his character entirely.

Mrs. Renauld then enters and confirms her husband was private about his youth, dismissing the idea of any great mystery in his past. When Stonor bluntly informs her that investigators believe Renauld was having an affair with Madame Daubreuil, her composure cracks. Through tears, she admits that Madame Daubreuil may indeed have been her husband’s mistress, a confession that leaves Stonor completely dumbfounded.

The interrogation is interrupted when a young man bursts into the room. He’s so strikingly similar in appearance to Renauld that Hastings is momentarily startled. The newcomer is Jack. He explains that his ship was held up by engine trouble and that he read about the murder in a newspaper before he could sail. Mrs. Renauld, upon seeing him, murmurs that it no longer matters that he didn’t sail.

Jack explains he was bound for Buenos Aires and then Santiago on urgent but unspecified instructions from his father, which were conveyed by telegram. After Giraud presses him, Jack admits he had a fierce quarrel with his father just before leaving during which he said he wished his father were dead. Jack refuses to name the cause of the dispute until Poirot calmly supplies that they argued over Marthe Daubreuil. Jack confirms it. He wants to marry Marthe, but his father forbade it without adequate explanation. Mrs. Renauld says she also opposed the attachment, citing Madame Daubreuil’s murky past. Jack denies any knowledge of the “Bella” letter or the name Duveen.

Hautet asks Bex to retrieve the murder weapon, but the dagger has vanished from the shed. Hastings confesses that he visited the shed earlier with a young woman and, after she fainted at the sight of the body, he forgot to relock the door for approximately 20 minutes. Giraud, rather than condemning him, calls the blunder useful because it proves the killer or an accomplice retrieved the weapon very recently. As the session wraps up and Poirot and Hastings exit, Poirot pauses to measure an overcoat hanging in the hallway.

Walking back to the hotel, Hastings reflects on Mrs. Renauld’s remark that it no longer mattered that Jack hadn’t sailed and concludes she knows more than she’s revealed. Poirot agrees and discloses that he suspected her from the start, given that she alone benefits substantially from the new will. He examined her wrists to determine whether she could have bound herself as part of a staged scene. The cuts from the ropes were genuine, ruling out self-inflicted restraints, though she could still have been an instigator with an accomplice.

Poirot believes someone moved the hands of her wristwatch forward to two o’clock and then smashed it to manufacture a false time of death. This would mean the crime occurred at least two hours earlier, and the fabricated timeline was designed to provide an alibi for someone who left Merlinville on the last train, at 12:17 a.m.

Poirot dismisses the story of masked intruders as a fabrication and calls the Santiago references a deliberate red herring. The South American cigarette and match, he says, were planted specifically for detectives like Giraud to find. He absolves Mrs. Renauld of direct guilt because her faint upon seeing her husband’s body was genuine. Even so, he asserts that she lied about the wristwatch, the masked men, and the open front door. Poirot believes the perpetrators left through the window and that their tracks were concealed by raking the flower bed smooth, which is why that bed, unlike the adjacent one, shows no footprints at all. Hastings realizes that Mrs. Renauld must be protecting someone.