Michel is an amateur gangster who, when we first meet him, is stealing cars in the French countryside. He is a free spirit who loves getting away with petty crime, but when he is cornered by a cop, he shoots him on the side of the road, and his problems start to get worse.
Michel goes to Paris where he asks various people for money and tries to catch up with a fellow petty criminal, Antonio, who has money for him. While in Paris, he reconnects with an American woman, an aspiring journalist named Patricia, with whom he has fallen in love. While she is meeting with an editor (with whom she is also having an affair), Michel procures her key and sneaks into her apartment. She finds him there the next morning and the two of them engage in a long conversation, at times professing their desire for one another and at others pulling away. Michel wants very badly to have sex and tells Patricia he's in love with her, but she is unsure if she's in love with him. She then tells him she is pregnant, most likely with his child.
Michel drives Patricia to her office, then to a press conference where she has been tasked with interviewing a famous novelist. The novelist is quite taken with Patricia and flatters her as she asks questions. Later, at her office, an inspector visits Patricia and asks if she's seen Michel, as she's been spotted with him and he's wanted for murdering a cop. She tells the inspector she doesn't know where Michel is, but takes his card to call him in case she encounters Michel.
Michel and Patricia meet up and spend a romantic evening together, first going to the movies, then stealing a car, then going to visit Michel's friend Antonio, who has money for him. They then go to a friend of Antonio's apartment to hide out and spend the night. The next morning, Patricia goes to run some errands, but stops at a cafe along the way to call the inspector and rat Michel out. When she returns to the apartment, she tells him she's turned him in, and that the fact that she had the impulse to do so is evidence of the fact that she doesn't love him. Michel gets angry at this flawed logic and opts not to make a run for it. Antonio gives him a gun, but he does not want to use it and instead runs from the police. After getting shot in the back, Michel looks up at Patricia and tells her, "You're a real louse," then dies. Patricia does not understand what he means.
