Due to financial problems, the boarding-school of Saint-Loup is on the verge of closing its doors. In desperation, Jacquelin, the headmaster, has the idea to invite former students to a fund-raising reunion. Among the alumni, three men whose common point is to have been in love at the time with the headmaster's niece. One is a banker, the second a priest and the last one a globetrotter. All of a sudden, the peace of the assembly is disturbed: Jacquelin's niece has just been murdered.

Jojo is a seventeen-year-old factory worker living poorly in Aubervilliers with his grandmother. Dissatisfied with his lackluster everyday life, Jojo dreams of the high life. He starts mixing with shady individuals such as thieves and traffickers. At a time, he even contemplates murdering a rich butcher. Fortunately, his protector Monsieur Charles, a warm-hearted gangster, will stop him from carrying out this crazy plan, thus wasting his young life.