Maxwell Anderson adapted the Colton-Randolph play of Somerset Maugham's story about the interaction between a loose woman and a reforming preacher on a south sea island.
Rain falls on a tropical island as soldiers march and sing. A ship arrives, and the passengers are detained for two weeks because of a cholera case. The trader Joe Horn (Guy Kibbee) accommodates Rev. Alfred Davidson (Walter Huston), Mrs. Davidson (Beulah Bondi), Dr. MacPhail (Matt Moore) and his wife, and Sadie Thompson (Joan Crawford). Sadie likes soldiers. Horn tells MacPhail he left Chicago for peace and hates reformers like Davidson. Sadie drinks and dances with soldiers. Mrs. Davidson complains, because it is Sunday. So Sadie takes them into her room. Davidson tries to stop it but is pushed out. Horn tells MacPhail that Davidson wants Sadie out. Sadie drinks with Horn and MacPhail and says Davidson went to the governor and reported Sergeant O'Hara (William Gargan). Mrs. Davidson shuns Sadie, and Davidson complains the governor won't act. MacPhail argues with him about what is right.
Davidson offers Sadie salvation and asks about her past in Honolulu, telling her to atone and saying she is evil. Sadie warns him. O'Hara visits Sadie, and Mrs. Davidson objects. Sadie tells O'Hara she doesn't want to return to the U. S. or Honolulu; he suggests Sidney. She gets a letter from the governor, ordering her to San Francisco. She complains to Davidson and appeals to MacPhail for help. MacPhail tries but does no good. Sadie explains she cannot go straight in San Francisco because of a politician; but he tells her to serve her three years punishment as atonement even if she was framed. She says he is bad too. Davidson prays, and Sadie joins in praying.
O'Hara gets out of the brig and tells Sadie to take the boat that night for Sidney; but she says no, because she must be punished to square herself for her sins, as Davidson says. She says she was born again, and Davidson arrives to rescue her from O'Hara. She says it was her fault, not O'Hara's, and Davidson says she has changed. After Horn and MacPhail say goodnight, Davidson visits Sadie, saying she doesn't have to go to San Francisco. When she says she will anyway, he calls her "a radiant daughter of the kingdom." During rain hearing drumming, Davidson agonizes and then goes into her room.
In the morning natives fishing find a corpse. MacPhail says Davidson committed suicide. He and Horn hear Sadie's phonograph and see her "dolled up." O'Hara tells her that Davidson cut his throat. Sadie decides to go to Sidney, and Mrs. Davidson says she is sorry for him and her. Sadie is sorry for everyone in the world.
This story exposes Christian hypocrisy and the sexist double standard about sexuality that Jesus forgave and tolerated and that has turned some, like Horn, from religion to Nietzsche. Davidson, because of his inner conflict, falls from social prominence and power to self-inflicted death, while Sadie, whose social position is the lowest, triumphs with the spirit of life.