Laurent Chevalier is a 14-year-old boy living in
Dijon in 1954 who loves
jazz, always receives the highest grades in his class, and opposes the
First Indochina War. He has an unloving father, Charles, a
gynecologist; an affectionate Italian-born mother, Clara; and two older brothers, Thomas and Marc. Thomas and Marc are inveterate pranksters, while Laurent engages in taboos such as shoplifting and masturbation. When Laurent discovers Clara has a lover, he is upset by the
adultery and runs to tell Charles, who, busy with his practice, angrily turns Laurent away. One night, Thomas and Marc take Laurent to a brothel, where Laurent loses his virginity to a prostitute, Freda, before they are disrupted by his drunken brothers. Upset, Laurent leaves for scouting camp, where he catches
scarlet fever and is left with a
heart murmur. Bedridden for a month, he is cared for and entertained by Clara and their maid, Augusta. Laurent's teacher at his Catholic school suggests that Laurent's illness has matured him, so that he has made progress in his studies, and urges Clara to treat him more like an adult. As Laurent requires treatment at a
sanatorium, he and Clara travel there and check into a hotel. Due to an error by Charles's secretary, the hotel books both Clara and Laurent into a single room, but, as the hotel is completely full, no additional room is available. Laurent takes interest in two young girls at the hotel, Hélène and Daphne, and also spies on his mother in the bathtub. Though Laurent pursues Hélène, Hélène says she is not ready for sex; Laurent later accuses her of being a lesbian. Clara temporarily leaves with her lover, but comes back distraught after their breakup, and Laurent comforts her. After a night of heavy drinking on
Bastille Day, Laurent and his mother have sex. Clara tells her son afterward that this
incest will not be repeated, but that they should not regret it. Laurent leaves their room, and, after unsuccessfully trying to seduce Hélène, spends the night with Daphne. When he returns to his room late in the morning, his father and brothers are there, having come for a visit, and immediately deduce what has happened. Clara enters the room, and the whole family breaks into prolonged laughter. ==Cast==