At a lonely military outpost on American Samoa, sticky heat alternates with torrential rain. A ship quarantine strands here Sadie Thompson, a "breezy dame" who sets the Marines afire... and self-righteous Mr. Davidson, powerful head of the Mission Board, who suspects Sadie is a fugitive from the notorious Emerald Club of Honolulu. Meanwhile, Sadie is courted by crude but good-hearted Marine Sgt. Phil O'Hara.