On a ship bound for Liverpool from the West Indies, the Anglican missionary's widow Olivia Harwood [Ann Todd] is pressed into service to help nurse malarial patients on the lower decks, her quiet resolve giving way to a growing curiosity about the mysterious Mark Bellis [Ray Milland], a suave passenger whose charm masks a life full of secrets. As the ship sails, their budding friendship deepens into something more intimate, with Mark’s easy smile and easy banter drawing Olivia into a fragile trust that feels like a lifeline.
When the voyage ends, Mark persuades Olivia to let him take up residence in the lodging house she has inherited from her late husband, and he devotes himself to a smooth, seductive campaign that catches Olivia off guard even as it charms Kitty Feathers [Moira Lister], a sharper, more worldly rival in Mark’s orbit. The situation grows increasingly dangerous as Mark’s past resurfaces: he reconnects with Edgar Bellamy [Raymond Lovell], his former partner in crime, and the two hatch a daring art heist. The plan goes awry, forcing them into a rooftop escape while police bullets narrowly miss their heels, a close call that leaves Olivia reeling and Mark triumphant in the boldness of his deception.
Back in Olivia’s circle, Mark convinces her that leaving London is the only way to secure a future together, and she, now entirely under his sway, abandons any remaining scruples to sustain the illusion. The couple moves into the Courtneys’ world, and Olivia is persuaded to insinuate herself into the home of her wealthy former schoolfriend Susan Courtney [Geraldine Fitzgerald] and her older husband Henry Courtney [Raymond Huntley]. Mark’s influence grows as Olivia is employed as Susan’s live-in companion, and she begins pilfering stocks, bonds, and small valuables from the Courtney household, turning the stolen goods over to Mark to convert into cash.
Hidden in the depths of the Courtneys’ correspondence are a set of letters from Susan to Olivia, recounting youthful indiscretions and moral lapses that Mark rightly believes could ruin the Courtneys’ carefully maintained respectability if exposed. The prospect of blackmail presents a tempting financial windfall for the pair, but Olivia’s conscience balks at crossing that final line. She flees the Courtneys and contemplates returning to overseas missionary work, only to discover that a lone woman is not welcome in that world, and she ends up sheltering in a somber church whose doors offer a fragile refuge. Mark tracks her there, and Olivia, drawn back into his orbit, submits to his control once more and resumes the blackmail scheme, even as she tries to pry herself free from the deepest layers of deceit.
Olivia’s actions finally draw the circle tighter: Henry, frustrated by Susan’s lack of an heir, schemes to have her committed to a distant mental asylum, while hiring a private detective [Leo G. Carroll] to trace the missing stocks and bonds and assemble a dossier on Mark’s criminal past. The situation erupts when Henry confronts Olivia with the breadth of Mark’s deception, a confrontation that unleashes a chain of events culminating in a heart-stopping collapse of the plan. Henry suffers a life-threatening heart attack, and Olivia cunningly persuades Susan to give him a dose of medicine laced with poison, leaving Henry dead and Susan facing the prospect of the gallows as the evidence points to her.
As Mark reveals his plan to take Olivia away to a new life in America, the truth she has avoided for so long becomes painfully clear: she has been nothing more than a pawn in his game. The moment of reckoning arrives when Olivia runs into Kitty, who is wearing the incriminating locket that ties Mark to the thefts and to her own complicity. The illusion shatters, and Olivia’s long-simmering realization crystallizes: her love for Mark was a carefully crafted ruse that masked a web of betrayal. In a final act of calculated retribution, she fatally stabs Mark in a hansom cab, then calmly walks into a police station to turn herself in, her conscience finally catching up with the consequences of her choices.
The drama weaves a taut, noir-tinged tale of desire and greed, where affection becomes manipulation and loyalty blurs into crime. Across its twists, the film delves into the corrosive pull of someone who uses charm as a weapon, all while tracing Olivia’s arduous path from naïve compassion to painful self-awareness.
