Due to an unfortunate turn of events, Georges de Kerlor is wrongly convinced that his wife has been cheating on him. Not only does he put her away but he also gets rid of little Jean, whom he believes (wrongly as well) is not his son. For a sum of money, he entrusts the poor boy to a petty criminal nicknamed La Limace (Slug). The latter and his wife Zéphyrine, who are already in charge of another brat, Claudinet, rename Jean Fanfan.