In a juvenile lockup, a new ward answers questions: she's Rosie, 13, no parents, a sister Irene, a brother Michel. In flashbacks we find out what happened. She lives with Irene, who's 27, whom Rosie knows is in fact her mother, but that's their secret. Irene's brother Michel, unemployed, a compulsive gambler, comes to stay with them. Around then, Irene meets Bernard; they come to care for each other. This leaves Rosie without attention, so she puts all her adolescent hopes and romantic fantasies into a relationship with Jimi, a good looking kid she sees on a bus. Is it adventures with Jimi that land her in juvie? Once she's there, why doesn't he answer her letters?