In 1985 suburban Paris, 12-year-old Vincent lives with his distant older brother and quarrelling parents. Amid laughter and unease, he navigates friendship and first love, while beginning to confront the adult world.

Diego Prince, 55, a world-famous former footballer turned coach, goes on holiday with his only daughter, Rosalie, aged 8. He confesses the truth to her: the existence of a son three years older than her, whom he doesn’t know and whom he didn’t want to have. Although Diego manages to shake off the burden of this secret, he doesn’t expect Rosalie to ask him to meet the boy. Father and daughter then welcome 12-year-old Billy to spend the rest of the summer with them...