Lee and Vivien Warren are caught in a tumultuous and destructive marriage filled with suspicion, infidelity, and emotional turmoil. Vivien, portrayed as despising, devious, and habitually unfaithful, constantly manipulates those around her, while Lee, haunted by pathological jealousy, struggles to maintain control. Their relationship unravels further when Lee returns from an extended business trip to New York, only to find that Vivien hasn't written or called him. His suspicion intensifies when he receives several cards addressed to Vivien, signed with the phrase "Love Always," which fuels his belief that she is unfaithful. Determined to uncover the truth or eliminate his doubts, Lee confronts Vivien's latest lover, Richard Fenton, an affair she has been involved in.
Fenton admits to his ongoing affair with Vivien, and Lee, driven by jealousy, persuades him to end things by writing a farewell letter to Vivien, implying that he is about to leave her. Lee then kills Fenton, staging the scene to appear as a suicide. He meticulously arranges the surroundings so the letter, written by Fenton at Lee’s insistence, looks like a genuine farewell note. Convinced that his plan is flawless, Lee believes he has committed the perfect crime. However, his confidence shatters when he learns that Fenton and Vivien had actually broken up some time before, and Fenton had only been humoring him, writing the farewell note as a joke or for some other reason.
Overcome with guilt for having murdered an innocent man, Lee realizes that the police, especially Inspector Penbury, question the plausibility of Fenton’s supposed despair, making Lee’s guilt harder to conceal. Meanwhile, Vivien has moved on and is now involved with a man named Jimmy Martin. Seizing an opportunity, Lee attempts to frame Jimmy Martin for Fenton’s murder, thinking that this would serve his interests by removing a rival and diverting suspicion away from himself. As he manipulates the evidence to point towards Jimmy, Inspector Penbury, played by Jack Warner, begins to suspect that not everything is as it seems, though he struggles to prove Lee’s guilt.
Vivien, desperate to save her current lover, pleads with Lee to intervene with the police to clear Jimmy Martin’s name. She promises her fidelity if Lee can devise a plan to free Martin without exposing himself. Lee, convinced that his innocence is at risk, agrees to cooperate, and they work together to change the narrative. Vivien then persuades Lee to write a letter, which she intends to be a suicide note, and she drugs him with his regular medication to hasten his death. During this act, Vivien confesses that she only loved Martin and had lied to Lee all along.
As Lee is near death, Vivien’s true motives become clear when she admits her deception. Her plan is to reunite with Martin, who, despite her efforts, refuses to see her and has reconnected with his supportive ex-girlfriend, Avis Fenton. Vivien’s attempt at emotional reconciliation fails, and she returns to her apartment, seemingly unfazed. Her demeanor shifts from a cover of distress to cold detachment as she is later arrested by Inspector Penbury for Lee’s murder. Her accomplice, Jimmy Martin, is symbolically given her engagement ring, inscribed “'til death do us part,” reinforcing the film’s themes of betrayal and despair.
The movie concludes with Vivien laughing cruelly, a chilling sign of her descent into madness and moral unraveling. Her laughter symbolizes her complete downfall, highlighting how her manipulative and ruthless personality has led her into a dark spiral of guilt, insanity, and moral ruin. The film leaves viewers contemplating the destructive power of obsession and deception, illustrating how greed, jealousy, and manipulation can lead to tragedy in a seemingly perfect facade of love.
