Mario, the head of the Mafia in France, has just been mortally wounded. His "companion" decides to find him a successor, before the New York "organization" appoints one. She instructs her two bodyguards to take on anyone who likes money, doesn't have any and, above all, doesn't want to work too hard - in short, "the average Frenchman"... They discover Léon Bonnet, a representative of "magic crosses". They send him gifts: champagne, weapons (a mistake...), a ring for his fiancée, and a meal worthy of the finest gourmets. In return, they take him to Mario's dying bedside, and have him sign over the estate. It's then that Leon, with his angelic good looks, restores order within the Mafia, surprising all his adversaries with his manners, and outwitting the police...

Antoine has raised Sébastien, the son of a friend who was killed in a plane crash. Sébastien is doing his military service and Antoine would like him to marry Nathalie, the girl he grew up with. But Nathalie is in love with an American, and the day Sébastien has a leave, she leaves with her lover.