Sir Thomas hopes that Fanny will begin to miss Henry in his absence. Particularly, he thinks she will miss the attention of being at the center of such a situation. Edmund is more realistic about Henry's chances, but he is surprised that Fanny does not seem to miss Mary, who has been her closest companion recently. In reality, Fanny is distraught that Mary and Edmund seem closer to marriage than ever before. William, on leave again, comes to Mansfield Park. He is not allowed to wear his new lieutenant's uniform off-duty, so everyone decides Fanny should accompany him back to Portsmouth to see the uniform while it is still new. She can visit her family as well. Sir Thomas, and to some extent Edmund, feel that being reminded of her "real" family's circumstances may induce her to accept Henry, in order to maintain her lifestyle and her standing at Mansfield Park. Fanny has not seen her family since she came to Mansfield as a child of ten, and she is happy to go. She also feels the separation from Edmund will do her good in preparation for his marriage. William warns Fanny that her father's home will seem rough in comparison to Mansfield, and that her parents and siblings are crude in their manners. Aware that Fanny's absence will be a hardship to his parents, Edmund delays his trip to London, the trip on which he is to propose to Mary. He tells Fanny of his plan to propose. Thus, her journey sees her both happy and distraught.
William and Fanny have an enjoyable journey to Portsmouth. She is worried still about Henry's addresses, since he has been writing to her via his sister, and William, aware of Henry's role in his promotion, wishes she would accept the man. Mary has been writing often. Fanny's mother is overjoyed to see her, but she is too busy to spend quality time with her daughter. The household is a mess: the children are dirty and ill-behaved, and Fanny's father drinks excessively. Fanny is well-aware of the niceties of behavior and environment to which her uncle's patronage have accustomed her. William has to leave almost immediately, as his ship has sailed early. Fanny's only consolation is her sister Susan, now fourteen, who is brash and lacking in manners but well-meaning, only needing guidance. Most of her other siblings are unruly beyond Fanny's capacity to influence them. Fanny reflects that the political doings of Mansfield are far less unpleasant than this chaos.
Fanny receives another letter from Mary which describes the London social whirl; Mary has been visiting with Maria and Julia. Fanny settles a quarrel between Susan and another of her sisters, which cements her relationship with Susan, who now looks up to her for guidance. Edmund has not written, which disappoints Fanny. One day, Henry Crawford shows up at Fanny's home in Portsmouth. He is introduced to the family as William's benefactor. He tells Fanny that Edmund has just arrived in London, where Mary is staying. Fanny is sure that Edmund has proposed by now. Henry insists on going for a walk with Fanny and Susan. On their way out, they encounter Fanny's father. Fanny has a moment of terror, sure that her father will behave crudely, but he is instead gentlemanly and offers to show Henry the Portsmouth shipyard. Henry manages to spend a little time alone with Fanny, who continues to resist his attentions. She is relieved that Henry cannot accept the dinner invitation her mother tenders him; she does not want him to see her vulgar, dirty family.
Henry appears the next day to go to church with the family, and they walk afterwards. He offers to take Fanny back to Mansfield, but she refuses. Henry tells her that he must leave to take care of business, and tells her a story about a poor tenant whose rights he seeks to protect. Clearly, he is trying to impress her. Fanny is in fact impressed and hopes that the "improvement" she sees in him means that he will cease his unwanted attentions to her soon. She is relieved that he is leaving Portsmouth.
Fanny's trip to Portsmouth is implicit punishment for her disobedience of Sir Thomas. It is a direct reminder that he has "made" her and that she can be returned to misery if she chooses to disobey him. Fanny's family shows all the effects of unfortunate circumstances, as Fanny's analysis of her mother shows: having a temperament similar to Lady Bertram's, Mrs. Price would have done well as a wealthy woman, but she has a difficult time managing a household for her drunk husband. Fanny's siblings are a reminder of the nineteenth century's interest in children and the nature vs. nurture question, which is directly relevant to the plot of this novel. Susan has a good nature and a level head, but she is trapped by her miserable family life. Only through the guidance of someone like Fanny can her essential goodness be realized. The other children, though, seem beyond Fanny's assistance. Fanny's siblings are meant to reflect on Mary and Henry, who have also suffered from bad guardianship as children. Although Edmund constantly excuses Mary's behavior on the basis of her upbringing, it is apparent that she is no Susan, that no amount of proper guidance could have molded Mary into someone like Fanny. On the other hand, left in her natural milieu, Fanny would have ended up much more like her siblings: undignified and crude (or perhaps she would not have lived at all, as her physical delicacy suggests). In the confusing, demeaning world of the Bertrams, she has grown up by necessity withdrawn and demure. Both one's essential nature and one's environment matter. At the same time, there are no absolutes in terms of environment, as Sir Thomas's coldness in exiling Fanny and Fanny's father's surprisingly gracious behavior toward Henry show; neither Mansfield nor Portsmouth is perfect. Fanny clearly sees Mansfield as her true family, though.
Henry's continued "improvement" seems more sincere when Mary is not around to expose his motives. That Fanny is almost swayed by his new attitude speaks to the quality of his dissembling. It also indicates just how vulnerable high moral principles like Fanny's are in a modern social world; under pressure for so long and faced with such a virtuoso performance, she is beginning to crumble. All forces seem to be aligned against her.