Lovers Florence Carala and Julien Tavernier devise a plan to kill Florence’s husband, Simon, a wealthy French industrialist who also happens to be Julien’s boss. Julien, a former Foreign Legion parachutist with a history in the Indochinese and Algerian conflicts, meticulously plots the crime. The two set their scheme in motion one Saturday when the office is quiet: Julien climbs the outside of the building using a rope and shoots Simon with Simon’s own gun, then collapses the scene as a suicide. He returns to his own office, leaving behind a set of false alibis—one secretary and one security guard who will stand with him as cover.
The moment of truth triggers a chain of unforeseen events. Julien, after stepping outside to his convertible, notices the rope still hanging from the balcony. He rushes back inside, boards the elevator, and waits as it rises. Unbeknownst to him, the security guard has already switched off the power and locked up for the weekend, trapping Julien between floors.
Before long, chaos shifts the plot in a startling way. Julien’s car is stolen by Louis, a petty criminal, and Louis’s partner Véronique, who works at a flower shop, becomes an awkward link to Julien’s life. Florence, waiting at a nearby café for Julien, spots the car pass by with Véronique leaning from the window and misreads the situation, fearing Julien could not go through with the plan and has taken up with Véronique. She drifts through Paris that night, searching urban bars and clubs with a desolate persistence born from love and fear.
Louis and Véronique drive Julien’s car and wear Julien’s coat, and Véronique finds Julien’s revolver in the glovebox. Their trail leads them to a high-spirited encounter with Horst Bencker and his wife Frieda at a motel off the highway after a race with a rival Mercedes. Frieda, curious and observant, photographs the couple with Julien’s camera, and later Véronique drops those photographs at the motel’s lab to be developed. The mood shifts dramatically when, in a moment of rushed fear, Louis kills Horst and Frieda with Julien’s gun after a tense confrontation.
Louis and Véronique return to Paris and hide in Véronique’s apartment, convinced they have escaped justice. Yet the weight of Julien’s supposed alibi and the evidence piling up—the appearance of Julien’s car, gun, and raincoat next to the Benckers’ bodies—drives the police to name Julien as the prime suspect. Julien himself, unaware of the morning’s front-page connection to the Benckers case, finally leaves the elevator and heads toward a café for breakfast, only to be recognized and arrested as the police dismiss his improvised alibi.
Florence refuses to accept Julien’s fate. She pursues Véronique’s address and arrives at Véronique and Louis’s place, where the exhausted couple sits in a daze. Florence confronts them, charges them with murder, and calls the police with an anonymous tip. Louis, feeling he has outwitted the authorities after seeing Julien’s photo, discovers that Véronique’s memory fades against the looming evidence—especially the film roll that still exists. He races to the motel’s photo lab, followed by Florence, but finds the photos have already been developed. Louis is arrested in a final twist of fate, while Florence enters the lab and confronts the shocking turn of events: the photographs on the roll reveal her and Julien together, exposing the lovers’ crime.
In the closing moment, Commissaire Cherrier presents Florence with the grim reality: she will likely face a harsher sentence than Julien. Yet Florence seems to drift into a trance, affirming that she acted for love and insisting that she and Julien will someday be reunited. The film closes on this resolute, unwavering belief, as the truth of their dangerous passion resonates through the room.
