The main character, Fanny Price, is a young girl from a large and relatively poor family, who is taken from them at age 10 to be raised by her rich uncle and aunt, Sir Thomas, a baronet, and Lady Bertram, of Mansfield Park. She had previously lived with her own parents, Lieut. Price and his wife, Frances (Fanny), Lady Bertram's sister. She is the second child and eldest daughter, with seven siblings born after her. She has a firm attachment to her older brother, William, who at the age of 12 has followed his father into the navy. With so many mouths to feed on a limited income, Fanny's mother is grateful for the opportunity to send Fanny away to live with her fine relatives.
At Mansfield Park, Fanny grows up with her four older cousins, Tom, Edmund, Maria, and Julia, but is always treated like a poor relation. Only Edmund shows her real kindness. He is also the most good-natured of the siblings: Maria and Julia are vain and spoiled, while Tom is an irresponsible gambler. Over time, Fanny's gratitude for Edmund's thoughtfulness secretly grows into romantic love. Her other maternal aunt, Mrs. Norris, the local parson's wife, showers attention and affection on her Bertram nieces, particularly Maria, but is verbally abusive and mean-spirited toward Fanny. She tries to exclude Fanny from outings and other pleasures, even denying her a fire in her room.
A few years after Fanny arrives, Aunt Norris is widowed, moves into a cottage of her own, and becomes a constant presence at Mansfield Park. Sir Thomas offers the parsonage to a Dr. Grant, who moves in with his wife.
When Fanny is 16, stern patriarch Sir Thomas leaves for a year to deal with problems on his plantation in Antigua. He takes Tom along hoping that the experience will sober him up. Meanwhile Mrs. Norris has taken on the task of finding a husband for Maria and manages to introduce this favourite niece to Mr. Rushworth, a very rich, rather stupid man. Maria accepts his marriage proposal, subject to Sir Thomas's approval on his return.
About this time, the fashionable, wealthy, and worldly Henry Crawford and his sister, Mary Crawford, arrive at the parsonage to stay with Mrs. Grant, their half-sister. After a year in Antigua, Sir Thomas sends Tom home while he continues business alone. Although his wife is indolent almost to the point of disengagement, Sir Thomas feels confident about his family situation, relying on the officious Mrs. Norris and steady, responsible Edmund to keep life running smoothly.
The arrival of the lively, attractive Crawfords disrupts the staid world of Mansfield and sparks a series of romantic entanglements. Mary and Edmund begin to form an attachment, despite her original preference for Tom as the heir of Mansfield Park. Although Edmund worries that her often cynical conversation may mask a lack of firm principle, and Mary is unhappy that Edmund wants to become a clergyman, their mutual attraction grows.
Fanny fears that Mary has enchanted Edmund, and that love has blinded him to her flaws. (Also, of course, she is in love with him herself.) Meanwhile, during a visit to Mr. Rushworth's ancestral estate in Sotherton, Henry deliberately plays with the affections of both Maria and Julia, driving them apart. Maria believes that Henry is falling in love with her and treats Mr. Rushworth dismissively, provoking his jealousy. Although nobody is paying much attention to Fanny, she is highly observant and witnesses Maria and Henry in compromising situations.
Encouraged by Tom and his friend Mr. Yates, the young people decide to put on Elizabeth Inchbald's play Lovers' Vows; however, Edmund and Fanny both initially object, believing Sir Thomas would disapprove and feeling that the subject matter of the play, which includes adultery, is not appropriate. Eventually Edmund reluctantly agrees to take on the role of Anhalt, the lover of the character played by Mary Crawford. Besides giving Mary and Edmund plenty of scope for talking about