A child bride holds her husband at bay while flirting with a sexy Italian farmer.

In the Mississippi Delta region, nineteen-year-old Baby Doll lives unhappily with her husband, Archie Lee Meighan, a middle-aged, down-on-his-luck cotton gin owner. Archie cannot afford to repair the decrepit antebellum mansion, Fox Tail, that the couple inhabits, and the Ideal Pay-as-You-Go furniture company is threatening to repossess their meager household belongings, thus giving Baby Doll more and more reason to malign Archie's masculinity. When Baby Doll was betrothed to Archie on her father's death bed, the dying man made Archie promise not to deflower the girl until her twentieth birthday, and with her birthday just two days away, Archie is anxious to make Baby Doll his wife "for real." As the childlike Baby Doll sleeps in her crib sucking her thumb, Archie tries to drill a hole in the wall in order to spy on her. Baby Doll awakes furious, and later during her bath, she becomes even more enraged when Archie tries to grab her. The next day, in town, while Archie is seeing his doctor about his sexual troubles, Baby Doll, determined to get a job, flirts with a young dentist who is looking for a secretary. As the couple returns to Fox Tail, they see the furniture being taken away, prompting Baby Doll to announce her desire to leave Archie and move to the Cotton King Motel. Meanwhile, Silva Vacarro, a Sicilian immigrant and the owner of the new cotton gin that has taken away all of Archie's business, gives his employees a fish fry to celebrate their first successful crop. As the festivities, which include a speech by a senator, ensue, a drunken Archie sets fire to Vacarro's cotton gin, burning it to the ground. Vacarro tries to tell the police that he was a victim of arson, but they treat him as an outsider and refuse to investigate. The next morning, Vacarro brings his twenty-seven loads of cotton to Archie's gin, and Archie is overjoyed to have the business. As Archie tends to the cotton, however, Vacarro meets Baby Doll and flirts with her in order to get information about Archie's whereabouts the night before. After Baby Doll reveals that Archie had indeed left her alone in the house on the previous evening, she grows suspicious of Vacarro, but he tickles and flirts with her to coax her to talk. Baby Doll gets nervous and goes to the gin to find Archie, but he slaps her and tells her not to go "where niggers are working." Vacarro is disgusted at the state of Archie's equipment and is furious that the work has not yet been started. He orders Archie to find a new belt for the cotton gin, but when Archie leaves, he is chased by a hysterical Baby Doll, who does not want to be left alone with Vacarro. After Vacarro's assistant informs him that they already have the belt, Vacarro approaches a weeping Baby Doll, who is upset because her live-in aunt, Rose Comfort, has left the house to go to the county hospital, where she satisfies her passion for sweets by visiting dying patients and eating their chocolate candies. Baby Doll explains her marital situation to a surprised Vacarro and then declares that her "being ready" depends on whether or not the furniture comes back. Baby Doll goes to make lemonade, telling Vacarro to wait on the front porch, but he sneaks into the house and begins to make ghost noises to scare her. When she locks herself in her bedroom, he makes the lemonade himself. The pair then begin a riotous game of tag and hide-and-seek, and Baby Doll locks herself in the attic. Annoyed, Vacarro tells Baby Doll that he will break the door down unless she signs the affidavit that he has prepared regarding Archie's guilt. He breaks in, and Baby Doll screams, fearing that the rickety floor of the attic will cave in. She tearfully signs the paper, then as Vacarro is about to leave, she offers to let him take a nap in her baby crib. Archie, meanwhile, is treated badly at the parts shop because he has no money and has to pay for the part with his gold watch. After he hurries back to the cotton gin and discovers that the repair has already been made, he returns home, only to be accused of arson by Baby Doll. She announces that their agreement is over, then Vacarro appears. Baby Doll reveals that Vacarro has decided not to rebuild his gin, but will bring the cotton to Archie's gin and have Baby Doll entertain him while it is being processed. Archie, confused, tells Vacarro to stay for supper while he considers his proposal. While Archie is on the phone, Baby Doll and Vacarro kiss, and then Archie, suspicious and angry, begins to scream at Aunt Rose to bring in the food. Archie decides to fire Aunt Rose, whom he claims has overstayed her welcome, but he is perplexed when Vacarro hires the teary-eyed old woman as his cook. Archie finally accuses the pair of having cheated on him, but Vacarro swears that he came for only one thing, the signed affidavit. Archie then calls Vacarro a "wop" and grabs his rifle. After Vacarro hides outside in a tree, Baby Doll calls the police and joins Vacarro in the tree. Archie, frustrated and exhausted after his rampage, finally breaks down in tears crying out Baby Doll's name. Once the police arrive and take the gun away from Archie, Vacarro emerges and shows them the affidavit, threatening to take it to the county sheriff. Before leaving, Vacarro promises to return the next day with more cotton. The town marshal then informs Archie that they must go through with his arrest for "appearances sake," and Archie watches Baby Doll go back to the house as midnight strikes, signaling her twentieth birthday. A transformed Baby Doll tells Aunt Rose that they will have to wait until the next day to see if they will be remembered or forgotten by the tall, dark stranger.