Agnes Huston, a widow, is discovered murdered in her own home, setting off a complex investigation that unravels through a series of interviews and flashback scenes. As Superintendent Lodge and Inspector Butler question her friends, neighbors, and acquaintances, they uncover widely differing perceptions of Agnes's personality and recent behavior, which complicate the case.
Mrs. Finch, Agnes's neighbor, paints a picture of her as a gentle and kind-hearted woman, contrasting sharply with her sister, Catherine Taylor, who comes across as rude, confrontational, and aloof. Mrs. Finch recalls a history of tension between the sisters, particularly about Agnes's husband having an affair, which led to a heated argument. Catherine reportedly left upset, but things escalated when, days later, she and her boyfriend, Bob Baker, stormed into Agnes's flat threatening violence. Mrs. Finch intervened, attracting the attention of Albert Pollard, a timid pet shop owner who describes Agnes as a sweet and helpful person, especially when she once asked him for help with her pet bird and later accepted his marriage proposal.
Catherine's account reveals a different perspective. She claims her visit to Agnes was marred by a rude greeting and an argument about accusations of infidelity, leading to her departure in anger. She admits to knowing Bob Baker, a magician who provided Agnes with a script for a mentalism act, which she says Agnes was supposed to practice but ignored. She also recounts their visit to Agnes, where she was treated disrespectfully and told to leave.
Baker offers his version of events, stating that Agnes was a kind-hearted but somewhat moody woman. He met her at her workplace, where she worked as a fortune teller, and described how she once tried to seduce him during a visit, which he refused. Their encounter turned sour when Agnes dismissed his romantic interest, and he notes that during the visit with Catherine, Agnes was disrespectful again.
Michael Murray, a sailor and Agnes's former lover, gives a more emotional account. He visited Agnes after months at sea, and they shared a kiss, indicating they had rekindled their relationship. However, when he saw her later with Albert Pollard, and suspected her of unfaithfulness—possibly involving prostitution—he reacted with anger and manhandled her, later feeling remorseful for his actions. Murray regrets not staying in touch and admits to being troubled by jealousy and suspicion.
Returning to Mrs. Finch's house for further questioning, Butler detects inconsistencies in Pollard’s account, especially after a neighbor mentions hearing the phrase "Merry Christmas," which Agnes had taught her bird. This clue, combined with other evidence, leads Lodge to believe that Pollard's story is fabricated. As they explore, Pollard is prompted to imagine a scenario in which Michael Murray, drunken and angry, might have entered Agnes's flat to commit the murder.
Lodge, piecing together the evidence and psychology behind the case, vividly reconstructs a scenario where Pollard, humiliated and overwhelmed by jealousy or rejection, might have strangled Agnes during a fit of rage. Convinced of his guilt, Pollard breaks down and confesses in a powerful, emotional scene, leading to his arrest. The investigation concludes with the realization that the case was driven by a mixture of jealousy, misunderstandings, and hidden passions, painting a complex portrait of Agnes and those who knew her.
