Kate Croy and Merton Densher are two betrothed Londoners who desperately want to marry but have very little money. Into their world comes Milly Theale, an enormously rich young American woman who had previously met and fallen in love with Densher, although she has never revealed her feelings. Kate welcomes Milly to London, and the American heiress enjoys great social success. However, after a visit to an eminent doctor, Milly discovers that she suffers from an incurable disiese.