Paul, a friendly Parisian cab driver, has two loves: music and his fiancée Virginie. After graduating from the Conservatoire with a first prize, he lives on hope, offering his classical works to publishers. One day, while driving customers to the races, he plays a "toquard": Maubeuge, who wins. With his friends, he celebrates the event and, for dessert, composes a song for the occasion: "Tout ça ne vaut pas un clair de lune à Maubeuge". Monique, a secretary at the radio station and one of the guests, had a record made of the tape recording. And this record, following a mistake, was broadcast on a religious music program. It's a runaway success: for Paul, it's fame and fortune. which he had obviously coveted, but more with his symphonies, opera and sonatas. No matter, the "Clair de lune à Maubeuge" (Moonlight in Maubeuge) allows two happily engaged couples to become happily married.

Un chauffeur de taxi amateur de musique et amoureux de sa promise connait le succès en écrivant la chanson "Un clair de lune a Maubeuge" suite à sa victoire aux courses.