The Mysteries of Paris - Volume 3 - Eugène Sue

Rodolphe, who is really the Grand Duke of Gerolstein (a fictional kingdom of Germany) but is disguised as a Parisian worker. He can speak in argot, is extremely strong and a good fighter. However he shows great compassion for the lower classes, good judgment, and has a brilliant mind. He is at ease in all layers of society and so is able to understand their problems, and how the different social classes are linked. (Summary by Michele Eaton )