Julie Kohler Jeanne Moreau attempts suicide by leaping from an upstairs window, but is stopped by her mother. After packing her clothes and a substantial sum of money, Julie says goodbye to her mother and leaves on a journey.
On the French Riviera, Bliss Claude Rich, a reformed womanizer, draws Julie in as she attends his engagement party at a high-rise apartment. He is instantly intrigued by her, and Julie lures him onto the balcony, dropping her scarf onto the awning support pole and convincing him to retrieve it in exchange for revealing her identity. As he climbs over the balcony, she tells him her name and pushes him to his death before she flees.
Julie’s next target is Robert Coral Michel Bouquet, a lonely bachelor. She persuades him to attend a classical music concert and agrees to meet the following night. Before their rendezvous, Julie buys a bottle of arak and injects it with poison. When she meets Coral at his studio apartment, she serves him the drink and reveals her identity. A flashback shows that the groom at a church wedding—Julie’s late husband—was shot to death; Coral insists it was an accident and pleads for his life before dying.
The next target is Clément Morane Michael Lonsdale, a would-be politician. After following his wife and young son, Cookie, to their suburban home, Julie befriends Cookie and tricks the wife into leaving with a fake telegram claiming that her mother is ill. Julie poses as Miss Becker Alexandra Stewart, a teacher, and offers to cook dinner for Morane and his son. She plays hide-and-seek with Cookie, discovers a small cupboard under a staircase, and later locks Morane inside to reveal her true identity. He pleads that what happened was an accident.
Another flashback reveals Julie’s husband was killed by Delvaux Daniel Boulanger, a member of an informal hunting club that also included Bliss, Coral, Morane and Fergus. After the rifle incident near the church, the men go their separate ways, swearing not to reveal their involvement. Remorseless, Julie seals the cupboard door and Morane suffocates. The real Miss Becker is arrested after Cookie tells the police that she killed his father, but Julie exonerates her with an anonymous call, claiming responsibility for the murder.
Julie waits in Delvaux’s junkyard, planning to kill him with a handgun, but he is arrested by the police for selling stolen cars. She then pursues Fergus Charles Denner, a womanizing artist, who becomes her model for a series of hunting-themed illustrations depicting the huntress Diana. He confesses his feelings for her, but she rebuffs him and eventually shoots him in the back. After discovering a full-length nude mural of her on Fergus’s wall, she contemplates painting over it but leaves it as is.
At Fergus’s funeral, Corey Jean-Claude Brialy recognizes Julie, a longtime acquaintance of Bliss and Fergus who had met her at Bliss’s engagement party. At the police station, she coldly confesses to murdering the four men, but refuses to disclose her motives. Julie is sent to the same prison as Delvaux, where, while helping the matrons serve meals, she hides a kitchen knife and uses it to stab Delvaux off-screen.
