Boulevard focuses on Georges 'Jojo' Castagnier, an adolescent who lives in a poor room under the roof of a block of apartments in the Pigalle section of Paris. He ran away from home when he realized that his step-mother hated him from day-one. Among Jojo's many neighbors is the gorgeous Jenny Dorr , a nightclub dancer, whose lover he dreams of being. But, to Jojo's disappointment, Jenny becomes the lover of Dicky, a former boxer, who spends his time loafing about the Pigalle cafés. Jojo lacks for steady work, but manages to meet his financial obligations with a series of odd jobs. He tries selling magazines, which is a success for a while, though posing as Narcissus for two gay artists proves to be something of a disaster. Eventually, he woos Marietta, one of his other neighbors and a girl more suited to his age. But when things go really awry, Jojo becomes desperate and tries to commit suicide by jumping off the roof of his building

Jojo vit seul dans une mansarde donnant sur la place Pigalle. Il tombe amoureux d'une danseuse, maîtresse d'un boxeur de seconde zone. Cet adolescent livré à lui-même découvre peu à peu le monde impitoyable des adultes.