Muichkine, a young Russian prince, returns home to St. Petersburg from a mental institution, determined to spread decency and kindness in the harsh and cruel world. He becomes betrothed to an innocent young girl while trying to save a less-innocent woman from her own travail, but jealousy and his own naivete conjoin to bring about unimaginable tragedy.

Paris, 1830. Fleur de Marie is rescued from poverty by the mysterious Rodolphe, who is in fact the Grand Duke of Gérolstein, who has gone incognito in search of an illegitimate child he once had. Which is not at all to the taste of Sarah Mac Gregor, her current mistress who kidnaps Fleur and has her locked up in Saint-Lazare prison.