While Sir Thomas is away, life at Mansfield Park is altered. Edmund is now the head of the household, and he continues to look out for Fanny, who is now eighteen years old. Edmund, for instance, declares that for her good health, Fanny should go horseback riding each day. Although his sentiment is good natured, Edmund fails to notice that Mrs. Norris discourages this. Mrs. Norris informs Fanny that the number of horses owned by the Bertram family is limited. If Fanny undertakes a daily routine of riding, that would mean either Maria or Julia would be deprived of the exercise.

Fanny gives in and spends most of her days serving both Mrs. Norris and Lady Bertram with errands around the house as well as walking long distances into the village. One day, Fanny becomes ill, which gains Edmund's attention. When Edmund discovers how Fanny's riding has been discouraged, he goes against his mother's and aunt's objections and purchases a horse for Fanny.

It is during this time that Mary and Henry Crawford move into the area. Mary and Henry are sister and brother to Mrs. Grant, the wife of the new clergyman. Mary is described as a beautiful woman, while Henry is only acceptably handsome. But Henry, it is noted, is very rich. Mary is searching for a husband. Upon meeting Tom, the elder Bertram son who has recently returned from the Caribbean, Mary decides it is he whom she must marry. She is not impressed with Tom in any way except for his money. Mrs. Grant chooses Julia as a possible bride for Henry, but Henry does not approve. Henry is more attracted to Maria, even though Maria has recently become engaged. Henry finds married or engaged-to-be-married women much more attractive.

Sir Thomas has remained in Antigua as his business there is not doing well. When he was sent notice that his daughter Maria wanted to marry Mr. Rushworth, a very wealthy but dull man, Sir Thomas gave his consent. Maria is delighted by her conquest even though she finds Mr. Rushworth overweight and somewhat boring. His estate is worth more than her father's, though. So Maria convinces herself that she can love this portly gentleman. In turn, Mr. Rushworth is pleased with Maria's beauty. Members of both families are happy about the engagement, except for Edmund. He can see that his sister appears to be joyful, but Edmund knows that her happiness is more centered on Mr. Rushworth's money than on the man himself.