Valerie Jennings, Andrea Allan, a London fashion model, travels into the countryside with her photographer boyfriend, Terry. He hopes to uncover something at a remote house, but he keeps the purpose to himself as they arrive at dusk. The house looms in nightfall, and inside Valerie discovers a bedroom full of numerous women’s passports, a clue that something dark has drawn them here. A couple enters the house—one woman and an unseen man—and panic spreads. Valerie and Terry hide in a closet, watching as the woman is suddenly stabbed to death with a switchblade. While the killer washes his hands in the bathroom, Valerie slips away, unaware that Terry is not following. When she realizes the car keys are missing, she flees into the trees and the killer pursues her into an abandoned wrecking yard, where she manages to vanish by climbing into a car and lying still.
The next day, Valerie reaches a road and hitchhikes back to London. She steps into her apartment and, at the kitchen window, sees Terry’s car parked on the street. The scene turns puzzling when she finds her modeling portfolio inside the unlocked car, with one photo missing. Confused, she heads to Terry’s flat, only to learn he has not returned home. Panicked, she seeks help from her friends, Mike and his girlfriend Stella. They urge her not to go to the police, fearing that involvement could implicate her in Terry’s supposed burglary. Later, at a modeling shoot, Mike introduces Valerie to his friend, Paul, a shy young artist who makes masks. Paul invites Valerie to dinner, where they are joined by his domineering Aunt Susanna. After Valerie leaves, this unsettling duo engage in incestuous sex.
Worried about Terry, Valerie agrees to bring Mike and Stella to the old wrecking yard, hoping to locate the missing man. They find Terry’s ravaged car there, but the house itself remains elusive. Valerie’s nerves are further unsettled by the presence of a new, eccentric neighbor below her—the enigmatic Mr. Hornby—who keeps pigeons in his home. She feels a touch safer when her flatmate, Lorna Collins, returns from a job away. But one night an intruder breaks into the apartment and murders Lorna after raping her, a brutal blow that deepens Valerie’s fear.
The murder prompts Valerie to go out of town with Paul, whom she now trusts enough to accompany. They drive to a remote manor house owned by Paul’s family, where he reveals that his father once took his own life in the very home. That night, Valerie hears noises from upstairs. Paul assures her no one is there, yet the eerie sensation intensifies as she notices a taxidermy animal identical to one she saw in the earlier house. She discovers a blood-stained bed upstairs and, as someone climbs the stairs, hides once more in a closet. Inside, she unearths the bodies of Terry and the first victim. Valerie bolts downstairs, only to be confronted by Paul, who attacks. Susanna urges him to finish her, but he turns on his aunt instead, stabbing her to death. Valerie bursts out into the night and is met by the approaching lights of the police. Inside the dark hallway, Paul sits in silence, the true danger still looming just beyond the door.
