A young woman, Ann, falls in love with and marries Doctor Robert Armour. She moves to Crow Hollow, the family estate, to live with his three eccentric aunts — a condition tied to keeping the property in the family.
From the start, Ann grows uneasy as a sequence of unsettling incidents unsettles the household. A large venomous spider drops from a box of delivered flowers while her hair is being styled by Willow; soon after, she becomes suddenly ill following a bitter-tasting soup served by Aunt Hester. Convinced that someone is trying to kill her, she grows wary of the house and its inhabitants, and the sense of danger deepens as the sense that she may be the next target tightens its grip.
Desperate to escape, Ann bribes the maid with a gift of clothes and slips out of the house with a suitcase, intending to board a train. Her friend Diana intercepts her before she can leave and persuades her to return. Back in her own bedroom, Ann discovers that the maid is dead—stabbed in the back while seated at the dressing table wearing the dress Ann had just given her.
The police arrive, question Ann, and express doubt about her theory that she was the victim, noting the difference in hair color between the two women. An old rumor surfaces, suggesting the maid, who had been adopted locally, might have been the child of a Crow Hollow gardener. The investigation imposes a hush on the house, with a rule that only Robert may leave Crow Hollow for professional calls.
Ann and Robert begin to form a theory: Willow had been wearing a hat at the dressing table to conceal her hair color, which supports their belief that Ann was the actual target. To help Ann cope with the pressure, Diana stays on in the house.
Opal discloses that there has been a call summoning Robert away to a medical case. Ann, wary of poisoning, refuses to drink coffee and deters Robert from leaving. In a tense confrontation, Opal admits that she had inadvertently killed Willow—her illegitimate daughter—whose plan had been to force Robert to marry Willow and thereby keep Crow Hollow in the family. Robert escorts Ann from the room, saying they will call the police.
Opal drinks the cup of poisoned coffee and dies. Outside the door, Robert tells his wife, “it's better this way.”
When the dust settles, Robert contemplates applying for a hospital post away from Crow Hollow, but Ann tears up the application and declares that she is now happy to stay, choosing the estate and its claustrophobic, protective circle over leaving it behind.
