Trama

A hippie girl wandering on a California beach is taken in by a Korean War veteran who lives in a nearby mansion with his sister. The girl soon begins to suspect that the mansion is home to some very strange goings-on.

In the opening scene, Robbin Stanley (Meg Foster) hitchhikes along a California coastal highway, she is given a ride by a young driver (Jesse Vint) in a hot-rod Model A Ford. His attempts to seduce Robbin compel her to ask the driver to let her out of the car. Instead, he presses the accelerator to the floor. Deputy Maynard Rakes (Stuart Whitman) pursues the car when it passes his speed trap, and notifies his superior, Sheriff Duke Bingham (John Ireland), who rushes to meet the deputy at a nearby roadblock. As he attempts to run the roadblock, the driver loses control and rolls his car. Robbin emerges unharmed while the driver is taken away by an ambulance. Deputy Rakes finds a bag of cocaine inside, but Robbin denies any knowledge of drugs.

After receiving a lecture on the dangers of hitchhiking from the sheriff, Robbin wanders onto a privately owned section of Arrow Beach. An unseen observer watches through a telescope as she swims naked in the ocean. Robbin falls asleep on the sand, but is awakened by the property owner, Jason Henry (Laurence Harvey), who invites her to have dinner with him and his sister, Grace (Joanna Pettet). When they enter the house, Grace takes Jason aside and reminds him of his promise not to bring any more women into their home.

While Grace cooks dinner, Robbin and Jason get acquainted in the study. She learns that he is an amateur photographer, and had been an Air Force pilot. Grace serves Robbin a very rare steak, in contrast to her brother's vegetarian meal. Over dinner, Robbin tells of how she has been traveling the country for the past 10 months, and that her parents have no interest in her. Despite an invitation from Jason to spend the night, Grace asks Robbin to leave, explaining that Jason is deeply disturbed and the presence of a house guest would be disruptive, but Robbin does not heed the warning. Grace cautions Robbin not to enter the basement, and to lock her bedroom door before retiring for the night.

Alone in his room, Jason is haunted by images of the Korean War, during which he resorted to cannibalism when he and his crew were stranded in the wilderness. Jason soaks a rag with chloroform and heads toward Robbin's room, but he is discouraged by Grace, who informs him that the girl's door is locked, and reminds him that his indiscretions could ruin their comfortable life together. Jason gives Grace two sleeping pills, and the brother and sister share a romantic kiss before saying good night.

Sometime later, Robbin hears a loud banging sound and follows it into the basement, where she finds Jason's photographic studio and darkroom, behind which is a door with a heavy latch. Upon opening it, Robbin discovers Jason, covered in blood and wielding a meat cleaver. She climbs to safety through a basement window as Jason grabs at her legs.

Following her escape, Robbin runs into town in search of help and collapses in a pool hall. She is brought to the sheriff's station with a large gash on her right arm, and her state of confusion leads Deputy Rakes to believe Robbin is under the influence of drugs when he admits her to the hospital. Meanwhile, Jason summons Sheriff Bingham to his home and hides the evidence of Robbin's escape. Upon the sheriff's arrival, Jason and Grace describe Robbin as a drug addict Jason took in as an act of kindness. Jason refuses to press charges, and asks Sheriff Bingham to return Robbin's bag to her when she is caught. Inside the bag, the sheriff discovers a small vial and a syringe... planted there by Jason to verify his story.

At the hospital, the doctor can find no evidence of drug use, and associates Robbin's symptoms with traumatic shock. Deputy Rakes is unconvinced and persuades the doctor to test for other kinds of drugs. Medical technician Alex Heath (David Macklin) hears Robbin scream and enters her room, where she tells him of her escape from Jason.

The following morning, Sheriff Bingham contacts Robbin's mother, who advises the sheriff to "throw the book at her." Instead, he orders Deputy Rakes to release Robbin and escort her out of town.

While his sister is away from home, Jason observes Ginger Tucker (Gloria LeRoy), an aging prostitute, on the beach through his telescope. He approaches Ginger while she is crying over being robbed by her last customer. When Jason introduces himself as a photographer, Ginger states that she was once a famous model and burlesque dancer. Jason pretends to recognize her and brings her inside to pose for him.

Meanwhile, at the hospital, after Deputy Rakes returns Robbin's possessions, she recounts her experience with Jason and demands his arrest. However, the deputy assumes that she is lying and orders her out of town. As Robbin leaves the hospital, Alex Heath begs her to stay with him, and although she declines, she writes down his address. Robbin takes a southbound bus out of town, then boards a northbound bus back to Arrow Beach at the next station. Meanwhile, Deputy Molly discovers that the drug planted in Robbin's bag is pyrellidex, a stimulant that was only used by the U.S. Air Force in the early 1950s, proving that the vial did not belong to Robbin.

In Jason's studio, Ginger poses enthusiastically for the camera before Jason hacks her to death with a cleaver. When Grace returns home and suspects Jason of murdering another woman, he placates his sister by promising to seek professional help.

At Alex's apartment, Robbin explains that she returned to Arrow Beach because, "I think Jason Henry kills people... girl people!" She and Alex break into the Henry house to gather evidence and make their way to the meat locker, where they find butchered human bodies. When Jason appears with his cleaver, he and Alex struggle until Grace shoots her brother. As Jason dies, Grace sobs, "He couldn't help himself."