 Henriette Deluzy Desportes becomes governess to the children of the Duc de Praslin. The jealous Duchesse spreads rumors of an affair between Henriette and the Duc. Finally she insists Henriette leave their employ, and fails to supply her with a promised letter of reference. When the Duc learns of this they argue and the next morning the Duchesse is found dead. The Duc takes poison and Henriette is forced to flee France. Facing a classroom of hostile students in New York, she tells them the story of "the notorious Mademoiselle D."