At the age of ten, Fanny Price is taken from the poverty of her childhood home and sent to live with her wealthy relatives at Mansfield Park in Northampton. Although she's aware of her debt of gratitude towards her aunt and uncle from the start, Fanny struggles to adjust to aristocratic protocol and the daily reminders of her inferiority to her relatives. Her spiteful Aunt Norris constantly reminds her that she will never be equal to the preening Bertram daughters, Maria and Julia, and her Aunt Bertram is too lazy to come to Fanny's defense. Her pleasure-loving eldest cousin Tom is often absent so her only real companion is her cousin Edmund.
Seven years later, Fanny's uncle, Sir Thomas Bertram, is on business in Antigua when brother and sister Henry and Mary Crawford come to the neighborhood, fresh from London society. Henry, who is a practiced flirt, sports with the affections of both the Bertram girls, causing jealousy between them. Maria is already engaged to the rich but stupid Mr. Rushworth, but this does not deter either her or Henry. Meanwhile Mary, who is attractive but has shaky principles, is drawn to the serious Edmund, despite him being destined for the church. An anguished Fanny watches as her beloved Edmund succumbs to her rival's charms.
On Sir Thomas's return, Maria quickly goes ahead with her marriage to Mr. Rushworth, determined to get her house in town and freedom from her father's restraints. She departs on her honeymoon, taking Julia with her. Henry now notices Fanny for the first time and fancies having her fall in love with him. But she loathes him and is not convinced of his sincerity. Her resistance only encourages him more, and with Sir Thomas's blessing, he proposes to her. Fanny refuses and Sir Thomas is furious — he cannot understand Fanny's determination to refuse Henry and encourages her to rethink her decision. As punishment, Fanny is left in solitude at Mansfield Park. Fanny now deeply misses Edmund and anxiously waits for news that he has proposed to Mary.
Before long, the family arrive home with Tom, who has caught pneumonia. As the family fear for his life, scandalous news comes from London: Henry and Maria have run off together. Mary treats the matter of adultery lightly. She shamelessly reveals her plan that she and Edmund will solve the problem with the help of Tom's inheritance, should he die. Edmund is horrified and tells Mary that the woman he thought he loved never existed. Finally, his eyes are opened and he realizes that he's been in love with Fanny all along.