Wynne Kinch, an adopted 14-year-old girl, Jenny Agutter harbors a crush on her 32-year-old stepbrother, George Bryan Marshall. From a charged start, she shadows him in a bathroom and notices scratches on his back. She also spots a jumper she knitted for him tossed into the rubbish, stained with blood—an unsettling clue that fuels her growing suspicion that he might be the local serial killer preying on teenage girls who remain at large. Even as this dangerous doubt gnaws at her, Wynne continues to entertain romantic fantasies about George and dreams of marrying him when she comes of age.
Throughout the film, she regularly visits the house she previously lived in with her adoptive family, a place that keeps echoing the memories of what she once had and what she imagines she could still attain. The routine visits sharpen the tension between perception and reality, as Wynne’s fixation slowly unravels the boundaries between affection, paranoia, and danger.
Later on, Wynne searches the back of George's van, hoping to find clues but is forced to stay inside and hide when he climbs in and drives off. He heads to a house, and Wynne discovers that he is having an affair with a mentally unstable woman, whose blood was on the discarded jumper after she had slashed her wrists in a suicide attempt. The discovery intensifies the sense that danger surrounds Wynne, and her internal conflict deepens as she weighs trust, danger, and the possibility that the man she admires may be capable of atrocity.
Wynne's best friend Corinne [Clare Sutcliffe] teases her about the crush on George, and during a family picnic Corinne flirts with him; he becomes irritated at her for acting like a "pathetic little mini-tart" and pins her down roughly on the ground. Corinne runs off and later phones Wynne to tell her she will stay out all night with an unnamed boy they both know. Worried about her friend, Wynne goes searching for Corinne at her former home and finds Corinne's dead body. About to leave the house, Wynne is confronted and trapped inside by the bus conductor [Simon Ward], a figure whom Wynne and Corinne often meet on the bus. He confesses to having killed the girls. Wynne tries to escape, he chases her and she falls into the pond. While helping her out, he breaks down in distress, and the police arrive to bring the nightmare to a close.
The film ends on a somber note as Wynne and George watch their old house being demolished, a stark visual reminder of how the past has reshaped their present and future.
