Camille, a 22-year-old man, takes up a job offer in Paris, so as to get to know the capital city. His employer turns out to be an extremely charming woman, Hélène Courtray, who has been separated from her husband for a number of years and is raising her son Pierre. Hélène's basic liberalism leads her to treat Camille as her equal. Camille's main role is to take meals to Pierre, who lives a reclusive existence on the 6th floor, a voluntary exile particularly hostile to his mother's chatter. As the days go by, an affectionate complicity grows between Camille and Hélène. She often asks the young man about his past, his family, childhood, his tastes in things. Little by little, Camille tells his story. And then, one day, Hélène disappears for three weeks. The day before her return, Camille gets the house in order, buys flowers and sets fire to the apartment with fierce determination. Hélène, who can't grasp what on earth possessed him to do such a thing, refuses to lodge a complaint and goes to visit Camille in prison. At the end of the visit, she's made up her mind: she will help Camille.