Una Spencer, a young woman, goes to the office of Peter Trevelyan, a manager at a large warehouse, to his shock.
Flashbacks reveal that Peter Trevelyan was once Ray Brooks, the next-door neighbor and trusted friend of Una's father. Ray groomed the 13-year-old Una into a three-month relationship. The two plotted to elope to Europe, but the night before they were set to board a ferry, Ray took her virginity in a coast hotel room. He leaves the room afterwards; Una, believing he abandoned her, wanders the streets distraught and bewildered, to be returned home by police after she shares what had happened to her.
Ray is arrested and serves four years in jail for his crime. Una grows up lonely and confused, believing she was in love with Ray and feeling more hurt by him abandoning her than by his abuse. She is ostracized by her peers and her father turns violent out of rage towards Ray before he passes away years later due to an accident at home. As an adult fifteen years later, she lives with her mother and takes solace in going out for one-night stands, unable to form lasting relationships due to the trauma of her abuse. Meanwhile, Ray, as Peter, finds success in his career and has since married. Una finds where he works through a newspaper photograph and travels to the warehouse.
After Ray brings her to the warehouse's locker room, Una, still emotionally wounded from the abuse, confronts him. Ray is dismissive and defensive and fears she may want to damage his career or even kill him. Ray leaves the room to attend a critical staff meeting, where he must announce cutbacks and layoffs to employees. Rattled by Una's presence, he instead tells his coworkers that management wanted him to generate a list of people to fire. He then leaves abruptly, and hides from angry executives and his fellow staff members.
Una finds Ray and they quarrel before reminiscing about their affair. Ray insists that he is not by nature a hebephile and was genuinely in love with her, and tells her that he is now married to a woman his age. To Una's surprise, he explains that he didn't intend to abandon her; he had needed a walk and a drink to clear his head before they would elope, but returned to find that she had left.
Unable to deny their lingering attraction to one another, Una and Ray have sex, but before it goes too far, Ray abruptly leaves, leaving her feeling abandoned once again. Ray tells his co-worker Scott, who is afraid of being laid off, to escort Una out of the warehouse. She invites herself to Scott's flat, where she seduces him. After preparing for a large party later that evening, Ray has sex with his wife Yvonne at home with his eyes closed. Meanwhile, Una claims to be "Pete's" daughter, and persuades Scott to escort her to Ray's comfortable suburban home after being informed about the party.
Upon arriving at the party, Scott quickly finds out that Una was lying upon introducing herself to Yvonne, and Ray is shocked to see Scott and Una arrive. Yvonne and Una talk briefly, and Yvonne hints that their marriage is not entirely happy. Una wanders upstairs, where she enters the room of Ray's 13-year-old stepdaughter and lies on her bed. The stepdaughter enters and demands an explanation why she is there. Una quickly leaves the house with Ray, Yvonne, and Scott following along. Ray approaches Una and denies her wordless accusation of possibly abusing his stepdaughter and insists again that Una was "the only one" before he kisses her on the cheek. Ray sees Yvonne, his stepdaughter, and Scott had been looking on from a distance. Realizing Ray is unapologetic, a disappointed Una leaves the party and walks off into the dark while Ray returns to his observing family and friends.
