In 1906 Paris, American businessman John Durham encounters his former girlfriend Fanny, who is now trapped in an unhappy marriage to a philandering marquis. Infatuated, John enlists the help of his American compatriots and Fanny’s mysterious sister-in-law, Madame de Treymes, to negotiate a divorce settlement. Madame de Treymes’ seeming willingness to help him turns out to be part of an elaborate plot by her wily and unscrupulous French family.