It's the story of spoiled, headstrong Julie Marsden (Davis), a flower of antebellum southern womanhood who treats men like playthings — particularly her equally headstrong fiance, Preston Dillard (Henry Fonda). She goes too far one night in her contrariness by wearing a red dress to the most important ball of the season, where all unmarried ladies are expected (naturally) to wear white. This turns out to be the last straw for Preston, who kicks Julie to the curb only to emerge a year later at the beginning of yellow fever season with a surprise Northern wife (Margaret Lindsay) a fine young lady who finds southern customs beautiful, strange, and slightly savage. The whole gang is reunited at Julie's country place (all right, it's a plantation) above the fever line, including roue Buck Cantrell (Brent), whom Julie decides to flirt with heavily while Preston is in earshot.
Eventually her flirting gets Buck killed in a duel on her behalf ( "We women can start the men quarreling often enough; we can't ever stop 'em."), Preston catches yellow fever, and Julie winds up redeeming her very bad behavior by promising Margaret Lindsay that she (Julie) should nurse Preston at the island of quarantine, for although southern women are treated like delicate flowers, they are strong and ruthless when they need to be... not like northern women with their talk of abolition and such.
As the patient, loving, and occasionally horrified Aunt Belle, Fay Bainter is truly the best thing in this picture. She's so much more natural an actor than Bette Davis, and thankfully, the Academy thought so too — she took home the Best Supporting Actress statuette that year and Davis won for Actress in a Leading Role. And hats off to the dependable Donald Crisp another sturdy performance as Dr. Livingstone (I presume).
Oh and it must have been excruciating to be an African-American actor in this era. I hope they were paid well, but something tells me...