Dany, a diligent secretary, takes up an unexpected offer from her boss, Michel Caravaille, to spend the night at his home to finish a project. Previously having worked with Michel's wife, Anita, he assures Dany that she would be glad to see her again. Upon her arrival, Dany becomes disheartened as Michel and Anita head out for a dinner party. Left alone, Dany dozes off and enters a disturbing dream where she kisses Michel, which quickly escalates into a nightmare as he begins to suffocate her. Dany's terrifying dream is abruptly interrupted by the return of Michel and Anita.
The following morning, Michel asks Dany to accompany them to the airport to drive back their luxurious car. Once left alone with the vehicle, Dany convinces herself that a little joyride to the coast won’t go unnoticed. Indulging in a shopping spree, she encounters a woman from a nearby café who asks if she is feeling better, to which Dany firmly asserts she hasn't been to any cafés.
After a stop for gas, Dany becomes a victim of an unseen attacker, injuring her wrist in the process. Although several men rush to her aid upon hearing her cries, one mechanic raises doubts, claiming she was already at his station the previous night with a wrist injury. Frustrated by the suspicion and feeling even more isolated, Dany insists on her innocence despite their skeptical glances.
Once she’s bandaged and back on the road, a police officer, already privy to her situation, stops her for driving with an injured wrist. He guides her to a hotel. When Dany questions the receptionist about her registration, she is taken aback to discover she is indeed listed as a guest. The attendant suggests her injury might have prevented her from signing in herself, further raising her anxiety about her sanity.
Venturing outside, she meets a man named Georges, who insists on hitching a ride with her. Initially hesitant, Dany finally agrees when he points out her likely theft of the vehicle. Sharing her unusual circumstances, Georges conjectures that the townspeople are merely playing tricks on her. When he learns Dany holds two reservations under her name, he slickly insinuates himself into the second room. As they flirt, passion leads to intimacy, but Dany soon discovers Georges’ passport bears a different name—a troubling revelation.
Eventually, Georges drives them to a picturesque location but vanishes momentarily. Realizing he has taken off with the stolen car, she attempts to hitchhike to the nearest town. With the assistance of a trucker’s CB radio, she locates her car. However, an eerie discovery awaits her in the backseat: a body along with a rifle. In a tense confrontation, both Dany and Georges accuse one another of murder. They agree to dispose of the body, but Georges finds a note that suggests Dany is the killer. Tensions rise, and in the ensuing struggle, Dany is knocked out when Georges overpowers her.
Regaining consciousness, Dany immediately calls Anita for help and confesses her involvement in the car theft. Anita instructs her to visit a friend’s house for safety, where Dany unexpectedly finds her missing coat. It isn’t long before Michel arrives and reveals a shocking truth: Anita had an affair that led to murder when the lover tried to blackmail her. Caught in a web of deception crafted by Michel, who intended for Dany to take the fall, the plan was to disguise Anita and stage a murder-suicide scenario. However, Dany's drive complicated their intricate scheme. In a climactic moment, Dany defends herself against Michel, eventually shooting him. The narrative concludes with her driving away, last seen swimming in the ocean, embarking on an uncertain future.
