Third Girl recap

Norma Restarick tells Poirot she may have murdered someone, then disappears after calling him too old. With Ariadne Oliver's help, he traces her to a flat shared with Claudia Reece-Holland and Frances Cary and to a family newly reunited with her returned father Andrew and his second wife Mary. Norma is repeatedly drugged and manipulated into doubting her memory; the death of Louise Charpentier and a staged attack on Norma's boyfriend David Baker are used to make her seem violent and insane. Poirot discovers that the supposed Andrew is Robert Orwell, an impostor, while Frances Cary also plays the part of Mary Restarick through disguise. The real Andrew died abroad. Orwell and Frances killed Louise because she recognised him and seek control of Norma's inheritance by having Norma declared incapable. Their reliance on roles that no one has seen together allows the deception to continue until Poirot reconstructs it. Norma is saved, the impostors are exposed, and David remains with her.

A young woman arrives at Poirot's flat and says she may have committed a murder, but she cannot name the victim or describe the act. She identifies herself only as a third girl, the last tenant added to a shared London flat, and abruptly leaves after deciding Poirot is too old to help. The remark wounds his pride, yet her uncertainty interests him more than a direct confession would. Ariadne Oliver recognises the description as Norma Restarick, a troubled young woman she recently encountered. Together they begin tracing Norma's household and associates before she can disappear completely.

Norma shares a flat with the capable Claudia Reece-Holland and the fashionable Frances Cary. Her father Andrew has recently returned from years abroad with a younger second wife, Mary, reviving the hurt caused when he abandoned Norma's mother. At the family home, elderly Sir Roderick Horsfield worries that his secretary Sonia has searched private papers. Norma's boyfriend David Baker, an unconventional artist distrusted by her family, offers another point of conflict. Poirot and Mrs Oliver hear competing claims that Norma is unstable, suggestible, or under a bad influence, but direct contact with her remains difficult and her movements are erratic.

A recent death begins to give shape to Norma's fear: Louise Charpentier died after falling from a London window, and links from her past reach toward people around the Restaricks. Inspector Neele and Poirot compare what can be established with Norma's broken impressions. Ariadne follows the younger social circle and places herself in danger by pressing too openly. Norma appears at times dazed or unable to account for hours of her life, suggesting either serious illness or outside interference. Poirot refuses to accept a diagnosis merely because the family repeats it, and asks who benefits if Norma comes to believe that she is capable of violence.

Mrs Oliver is attacked while pursuing a lead, confirming that the inquiry has disturbed a deliberate plan. Norma's recollections blend genuine events with images that may have been arranged for her to see while confused. The people around her offer apparently reasonable explanations, but their accounts depend on accepting family and household identities at face value after long absences. Poirot examines the shared flat, the Restarick home, and the connections between Louise Charpentier and Andrew's years abroad. David's relationship with Norma remains suspect to the family, though his conduct does not fit neatly with the pressure to have her treated as insane.

Norma is subjected to another terrifying scene involving David, blood, and a weapon, leaving her ready to believe that she has attacked him. Poirot recognises that the incident is staged and that drugs have repeatedly weakened her ability to separate memory from suggestion. The intended outcome is not merely to frighten her but to produce witnesses and behaviour that justify taking away her legal independence. He focuses on people who occupy two social settings and on the fact that certain members of Norma's circle are described as distinct without being reliably seen together. Louise's recognition of someone from an earlier life supplies the motive for the real death.

Poirot exposes the supposed Andrew Restarick as Robert Orwell, an impostor, and Frances Cary as his accomplice. Frances has also impersonated Mary Restarick, altering her appearance and arranging movements so that Norma's flatmate and stepmother seem to be separate women. The real Andrew died abroad. Orwell and Frances seek control of Norma's inheritance by drugging her, breaking her confidence in her own memory, and staging violent scenes that will support having her declared insane. Louise Charpentier recognised Orwell and was killed to protect his assumed identity; the conspirators then directed Norma's confused fears toward that murder. The apparent stabbing of David was another manufactured scene rather than Norma's act. Poirot's reconstruction of the doubled identities and the chemical manipulation saves Norma and defeats the plan. David's concern for her is genuine, while Sir Roderick's anxiety about Sonia and his papers proves peripheral to the murder scheme.

Poirot establishes that the man presented as Andrew Restarick is an impostor, Robert Orwell, and that Frances Cary is his partner. Frances has also been appearing as Mary Restarick, using changes of clothes and appearance so that the flatmate and the supposed stepmother seem to be two women. The real Andrew died abroad. Orwell and Frances intend to gain control of Norma's inheritance by making her appear dangerously insane. They drug her, exploit her fragmented memory, and stage incidents around her, including the apparent stabbing of David Baker, so that she will believe herself capable of murder. Louise Charpentier recognised Orwell from his earlier life and was killed to protect the impersonation; Norma was manoeuvred into believing she might be responsible. Poirot's attention to identities that are accepted without independent recognition exposes the arrangement. Norma is rescued from the attempt to complete the scheme, the false family structure collapses, and David's attachment to her proves genuine. Sir Roderick's suspicions about Sonia and his papers belong to a separate, less murderous deception and do not explain Norma's ordeal.