On vacation in Scotland, Geoffrey Carroll is unexpectedly confronted with the truth that the man she’s been seeing, Sally Morton Carroll, has a lover who is already married to an invalid. She ends their affair, and when she returns to London, Geoffrey is living with his wife and their pre-teen daughter, Beatrice, while he works on a portrait of his wife that starkly depicts her as the Angel of Death. The mood darkens as Geoffrey’s art sustains his success, yet he suddenly finds himself creatively stunted.
Two years pass, and Sally is pulled into a new social circle when her former fiancé, lawyer Charles Pennington, arrives with his wealthy client, Mrs. Latham and her icy daughter, Cecily Cecily Latham. Cecily asks Geoffrey to paint her portrait, and the studio begins to fuel an affair between painter and muse. Behind the scenes, Horace Blagdon — a chemist deep in debt from horse racing — tracks Geoffrey down and uses blackmail to extort money, tightening a dangerous noose around the couple.
Meanwhile, Sally endures episodes of weakness and pounding headaches, which she suspects are not simply nerves. The local doctor, Dr. Tuttle, treats her with a practiced, if bumbling, calm, misreading her condition as fatigue rather than danger. Cecily, poised and calculating, confides that she plans to depart for South America and invites Geoffrey to accompany her, deepening the rift between Geoffrey’s loyalties.
Geoffrey travels to London to secure the balance Blagdon demands, while Sally discovers Bea is packing for boarding school—a detail Geoffrey had never mentioned. Bea’s story hints that Sally was healthy until Geoffrey’s return from Scotland, casting doubt on whether Sally’s symptoms were real or manufactured. In a chilling moment, Sally and Bea enter Geoffrey’s studio and uncover a new painting—the portrait of Sally as the Angel of Death that haunts them both.
The tension crescendos as Geoffrey, having only secured part of Blagdon’s money, murders the chemist to silence the threat. The sense of danger spills into the dinner party that night, with Geoffrey poised between confession and flight. When he returns home, he informs Sally that he plans to tell her everything and run away with Cecily to South America. The maid helps Bea prepare for boarding school, and Sally, wary of Geoffrey’s schemes, refills her resolve.
Geoffrey begins to stalk Sally in a final bid to erase the evidence of his crime, and he cuts the phone line after she tries to summon help. He breaks into the bedroom, confessing that she no longer inspires his work and that she must die so he can discover a new muse, admitting this has happened before. Penny [Charles Pennington] arrives with two police officers just as Geoffrey closes in. A tense struggle unfolds, and the officers intervene, leading Geoffrey away as Sally pleads for calm. In a final, grim moment on the staircase, Geoffrey flatly asks if they would like a glass of milk, but the officers decline, sealing his fate.
