Here is the story of the « Mysteries of Paris » : The Prince Rudolph of Gerolstein is looking for the young Germain, the son of his housekeeper, dealing with the underworld of the Ile de la Cité area. There he meets Fleur de Marie, a young prostitute, and he will realise, after many adventures, that she is his daughter, whom he thought dead. But before we get there, he will investigate among the good and (especially) the wicked, colourful characters from the various Paris circles: the working classes, the petty bourgeoisie and the aristocratic Paris.