This section sets up all the main characters and introduces us to many of them as children before quickly aging them into young adults. We learn how the Bertram family functions and the author sets up Fanny's awkward place in the family, as well as her important relationship with her cousin Edmund.
In this stage a number of complicated romances emerge, all centering around the Crawford siblings. While Sir Thomas is away, his kids start running amuck and get involved in a scandalous theatrical production that allows for lots of flirting.
After Maria's marriage, she and Julia leave and the main cast of characters shrinks considerably. We start to focus on the increasingly complicated relationships between Mary, Fanny, and Edmund. Henry returns in this stage and starts to pursue Fanny just to gain another conquest, which leads to more problems.
Fanny's refusal of Henry's sincere marriage proposal causes a series of climaxes as Fanny has to talk with nearly all the major characters about her choice. The major climactic scene occurs during her confrontation with Sir Thomas over her refusal of Henry.
Fanny is under siege from Henry and her entire family, who think that she ought to marry Henry. Edmund's relationship with Mary seems like it's heading towards marriage, which depresses Fanny. Fanny is also sent to Portsmouth, which is a dramatic change of scene for her.
While Fanny is miserable in Portsmouth, her cousins are all suffering greatly in their own ways: Tom is dangerously ill, Maria scandalously runs off with Henry, Julia elopes, and Edmund breaks up with Mary. In the midst of this turmoil, Fanny returns rather triumphantly back to Mansfield Park and is welcomed by her aunt and uncle.
Fanny and Edmund finally marry while a lot of the major characters, like Maria, Henry, and Mary, end up alone.