Bree Daniels, portrayed by Jane Fonda, is a New York City prostitute with dreams of becoming a model and actress. She previously worked with Jane McKenna and Arlyn Page under the control of her pimp, Roy Scheider. After a frightening encounter with a violent client, Bree decides to leave her life of full-time prostitution behind.
The film opens with Tom Gruneman and his wife hosting a social gathering at their home in Tuscarora, Pennsylvania. Among the guests are Tom's colleague, Peter Cable, and his friend, the policeman John Klute.
Suddenly, Tom disappears without a clue, prompting an investigation by the authorities. During their search, they discover a lewd letter addressed to Bree at Tom’s office. When contacted, Bree confirms she’s received multiple letters but fails to recognize Tom from a photo presented to her. She's subsequently arrested for prostitution but, upon her release, she severs ties with her pimp and starts to work independently. She relocates from Park Avenue to a more modest apartment, growing increasingly paranoid that someone is trailing her.
After six months with no leads on Tom Gruneman’s case, the police hit a wall. Consequently, Peter Cable engages John Klute to journey to New York and resume the investigation. Klute takes up residency in the same building as Bree, tapping her phone to gather evidence. He later reaches out to her for assistance in uncovering the mystery of Gruneman's disappearance. Although she is initially hesitant, Bree’s cooperation grows as Klute offers her protection against the unknown stalker.
She attempts to seduce Klute to exert control over him, yet soon develops genuine feelings for him when he aids her in escaping from her former life. As Klute digs deeper, he discovers troubling links between Bree and two other former prostitutes, Jane McKenna and Arlyn Page. Both women have met tragic fates, with Jane apparently committing suicide while Arlyn is found dead after Klute tries to track her down.
As Klute pieces together the puzzle, it becomes evident that Bree, Jane, and Arlyn were all victims of the same man who exploited them. This individual not only used Tom Gruneman's identity while with the women but is also suspected of murdering them.
Ultimately, Klute’s investigation leads him to uncover Peter Cable as the likely culprit, indicated by distinct typing errors found in the obscene letters sent to Bree. Viewers learn that Cable has been observing the horrific acts through recordings, building a chilling portrait of a twisted psyche.
Toward the film's climax, Cable confesses to Bree that Tom had caught him with Arlyn, leading him to plant the letter in Tom’s desk to mislead the investigation. However, it remains unknown why he would enlist Klute to continue when police efforts had stalled, or if he subsequently killed Gruneman.
In a final confrontation, Cable attempts to murder Bree, but Klute intervenes just in time, resulting in Cable’s fatal tumble from a window. With newfound hope, Bree prepares to leave her apartment to start a life with Klute, who she has grown to love, though she harbors doubts about leaving her past behind for a conventional future.
