Thirty years ago a Miss Maria Ward married a guy named Sir Thomas Bertram. She became Lady Bertram and the two lived in Sir Thomas's fancy pad, Mansfield Park.
The former Miss Ward had two sisters. One married a reverend named Mr. Norris who didn't have a ton of money, but wasn't poor.
The last Miss Ward, Frances, had the worst marriage of all – she wed a poor sailor named Mr. Price, who became poorer and drunker as the years went by.
The Ward sisters grew apart accordingly. Frances had defied her family when she married the sailor, and Mrs. Norris and Lady Bertram didn't speak to her for years.
Eleven years later, Mrs. Price had a really big family (eight kids with a ninth on the way) and not enough money to deal with all the kids.
So she wrote to the Bertrams to ask for some help. She wanted to send her eldest son to live with the Bertrams to work for Sir Thomas.
The Bertrams didn't want the kid, but they did send letters and money and advice.
Mrs. Norris decides that Mrs. Price could really do with one fewer kid and proposes that Sir Thomas let the eldest Price daughter, age nine, come live at Mansfield.
Sir Thomas hesitates because he's heard stories about cousins falling in love and doesn't want some random poor cousin marrying one of his sons. Mrs. Norris laughs this off. The audience laughs, too, at the foreshadowing here.
Mrs. Norris rambles on and on and on and in a nutshell says that the little Price girl will grow up like another sibling to the Bertram boys, which means they certainly won't be getting married.
Sir Thomas is finally convinced and says they can send for the girl.
Mrs. Norris manages to finagle her way into a road-trip and offers to go pick up her niece herself, making it sound like a big sacrifice on her part when she totally wanted to take a trip anyway.
But Sir Thomas was somehow under the impression that Mrs. Norris was going to help out with the little Price girl, but Mrs. Norris had no intention of doing that since kids are expensive and Mrs. Norris is stingy.
Sir Thomas is surprised to hear that Mrs. Norris wanted nothing to do with actually raising the kid and says that the girl can just come live at Mansfield full-time.
The Bertrams and Mrs. Norris discuss their niece's disposition and hope she won't be too much trouble for them.
Sir Thomas notes that the girl will have to be brought up as not quite equal to her cousins since she isn't really a Bertram, but that the family shouldn't be mean to her or arrogant regardless.
So Mrs. Norris writes to Mrs. Price to tell her the plan. Mrs. Price is surprised they want a girl and not a boy, but she shrugs it off and prepares to ship her kid off to Mansfield. Presumably no one has bothered to ask the girl if she is cool with this plan or not.