Émile Durand, an insecticide manufacturer, is appalled to learn that his son Gérard has fallen in love with Suzy, the daughter of a travelling theatre company. Realising his father will never favour the union, Gérard joins the company on their next tour. In an attempt to heal the rift, Durand’s wife goes after Gérard and ends up performing in their next play…

The evocation of Paris in the 1920s mingles with the rapid rise of the irresistible Caprice, a talented singer, and her tumultuous love affair with Jeff the composer. A photographer nicknamed Bagnolet, a gentle anarchist, gently monitors the activities of Caprice, who has become Lady Paname and, in the absence of morality, makes love triumph.

Maurice Vallier, nicknamed "Ma Pomme"(which means "myself" in slang), is a cheerful man, well aware that money does not make happiness and who, of all things, prices freedom. Which is why he has become a tramp and he has never regretted his choice of life. Things go smoothly until the day he inherits a huge amount of money. He first refuses it but changes his mind when he realizes that thanks to the inheritance he can help others. Even more enticing is the fact that he must share the big money with a charming air hostess. However once he deems he has done enough good he gives up the money left and resumes his old lifestyle singing along "Ma pomme c'est moi, j'suis plus heureux qu'un roi..."

Benoit, the head guard of Clouville Prison, prefers to be liked than feared. This basic principle transforms the jail-house into a joyful prison, where all the inmates live amicably together. Among them, various colorful characters : a farmer, a poacher, a distiller, a forger, two pickpockets, a safe-cracker, a gangster and... a good-looking guy who pleases Rosette, Benoit's daughter, well. But too much leniency takes its toll : after Vauclin, the gangster, manages to escape and a complaint is filed against "the deplorable disorder reigning in the joyful prison", Benoit is given early retirement. He will know how to take advantage of his new status live a joyful life with his wife, his daughter and André, his son in law, in fact the nice-looking young prisoner who, in the meantime, has been cleared of all charges.