Fanny Price, the eldest daughter in a family with little money in Portsmouth, is taken in by her well-to-do uncle, Sir Thomas Bertram, who lives in Mansfield Park, a large residence in Northamptonshire.
She is brought up there, with the company of her cousins Tom, Edmund, Maria and Julia, all of whom are older, stronger and more confident. Her aunt, Lady Bertram, also lives there, and her other aunt, Mrs. Norris, occupies the local parsonage.
Time goes by, Mr. Norris dies, but Mrs. Norris still lives locally. Fanny is generally treated as a poor relative by everyone except Edmund, for whom she develops an attachment. She reaches 18, and all the cousins are similarly of a marriageable age. Dr. and Mrs. Grant arrive to take occupancy of the Parsonage, Sir Thomas leaves to deal with problems on the estate in Antigua, and takes Tom, the eldest son, with him.
And now the action gets going... Mr. Rushworth, a very rich, stupid, fat man, takes a shine to Maria, there is a courtship established and they are more or less engaged, only waiting for Sir Thomas to return to get his consent. Henry and Mary Crawford, brother and sister to Mrs Grant, arrive at the Parsonage. Henry flirts with both Julia and Maria, and Mary and Edmund begin to form an attachment.
A trip to Sotherton, Mr Rushworth's home, is organised. After the usual neglect of Fanny, it is arranged so that they all go there. While at Sotherton, there is much talk of 'improvement' - it turns out that this is a skill of Henry's - and Maria and Henry flirt outrageously, even going for a very suggestive and rather improper walk in the wood.
Edmund and Mary also develop their relationship, even if Mary does make an ill-judged comment about the clergy and says, tellingly, 'resting fatigues me'. Fanny, of course, observes silently, judging both Crawfords in a very harsh light indeed - Mary is all wrong for Edmund and Henry is simply all wrong.
Tom returns, a friend in tow, John Yates. It is decided to stage the 'theatricals' at Mansfield Park. Fanny and Edmund are violently opposed, especially when the play chosen, Lover's Vows, is highly improper - and they know that Sir Thomas would not approve. Everyone else gets involved and even Edmund has to join in, playing the lover of Mary Crawford.
Henry and Maria flirt like mad; Julia gets cross; Mary and Edmund start to get excited; and Fanny, disapproving every step of the way, becomes intrigued - Henry, by the way, is much the best actor. Just as they're about to get going with a proper rehearsal, Sir Thomas comes back, does not approve - and the theatricals are cancelled.
Henry leaves Mansfield Park, Yates goes too, and Maria marries Mr. Rushworth. The Rushworths then go off to Brighton, and take Julia with them too. Mary and Edmund continue to flirt, circling around each other and confiding in poor, tortured Fanny. Mary is still too worldly; Edmund is still too principled. Henry comes back and, for a bit of fun, decides that he will make Fanny fall in love with him. The tease...
Fanny's brother William, on leave from the Navy, comes to Mansfield Park for a visit and the two of them have a great time, Henry doing all he can and Edmund and Mary still dancing around each other. And then a Ball is arranged at the house on the night before William goes (Fanny's ball) and Henry is most ardent in his attentions. Everyone notices. But still nothing is settled between Mary and Edmund.
Henry and William go away and Henry is soon back with the news that he has managed to get his uncle, the Admiral, to exert some pressure in favour of William, and that William has been given a commission as Second Lieutenant.
Fanny is delighted, of course, and we find out that Henry is now determined to marry Fanny. He proposes and, much to everyone's astonishment, she refuses. Edmund and Sir Thomas put pressure on her, and Henry refuses to give up. This goes on and on, and Edmund and Mary are still boring everyone with their courtship. Eventually, William comes up for another visit, and Fanny accompanies him back down to Portsmouth.
Fanny hates her noisy, inconsiderate family in Portsmouth. Meanwhile, Edmund is in London, as are all the other younger characters. Nasty place, London. Henry pays her a visit, and actually has her wavering in her determination not to marry him. Then Fanny hears the terrible news that Tom is dangerously ill, due in part to his drinking and otherwise terrible lifestyle.
After a while (Fanny has now been there 3 months) this is followed by a letter from Mary, a newspaper report suggesting that Mrs R and Mr C have disappeared together, and a letter from Edmund confirming it. Fanny and her sister Susan are rushed up to Mansfield Park, where they learn that Henry and Maria have run off, Julia has eloped with Mr Yates and Edmund and Mary are completely split asunder. Oh dear.
Maria and Henry get tired of each other, and Sir Thomas arranges for Maria to live, with Mrs Norris for company, in 'another country'. Julia and Yates are to be married. Then Edmund takes his nose from his navel, sees Fanny and they're married too.
Tom has recovered and is now born again as a responsible person, the Grants move out of the Parsonage, Edmund and Fanny move in, and Susan takes Fanny's place, looking after Lady Bertram. And Sir Thomas is happy. At last.