Fanny, still distressed by Tom and Mrs. Norris's attack on her, retreats to the old nursery where she keeps her books and other possessions. Edmund comes to ask for her advice. Having found out that Tom intends to ask a neighbor to take the remaining part in the play, he has resolved to take the part himself rather than allowing an outsider to take part in and witness the production. He is also aware that Mary Crawford is unhappy about having to play opposite a stranger. Fanny is unable to give her full consent to Edmund's plan, but she reluctantly agrees that his idea is probably for the best. Inwardly, she is in turmoil; she cannot believe that Edmund has agreed to act, and she blames Mary for leading him astray.
Rehearsals continue. To Fanny's relief, Mrs. Grant takes the part Tom tried to push on Fanny; Mary has saved Fanny once again. It has become increasingly obvious to all, particularly to Mary and Mrs. Grant, that Maria and Henry are interested in one another, despite her engagement to Rushworth. Mary criticizes Maria for trifling with a man with such riches; he might "escape a profession" and simply live as a gentleman, Mary notes. Both Mary and Mrs. Grant agree that Sir Thomas's return will help immensely, by bringing back some much-needed common sense and authority.
Fanny becomes the confidant of all involved in the play and hears all the gossip and complaints. She is also valuable as a rehearsal partner and acting coach, although she is unwilling. Henry and Maria both prove to be fine actors, and Fanny cannot help but admire their talent. Rushworth is an inept actor and an annoyance to all, and Fanny must tolerate the others' complaints about him as well as his constant requests for a rehearsal partner. The time soon comes for Edmund and Mary to rehearse a scene together in which their characters make declarations of love for one another. Fanny is dreading its performance. As she hides in the former nursery, Mary seeks her out and asks her to rehearse the scene with her. Just as she reluctantly agrees, Edmund arrives, to ask the very same favor of Fanny. Edmund and Mary happily decide to rehearse together, with Fanny as audience. The emotional strain is nearly too much for Fanny.
Finally, the time comes for a dress rehearsal. Mrs. Grant must stay at the parsonage to care for her sick husband, and the group pressures Fanny to read her part. Even Edmund urges her to cooperate. She is forced to yield, and is about to begin the reading when Julia, who is still not participating in the play, rushes in with news that Sir Thomas has just arrived at the house.
Everyone's alarm at the return of Sir Thomas is a signal that they know they are doing wrong in performing the play. That even Fanny has been forced to take a part suggests the potential destruction involved in the performance; it has slowly corrupted every part of the household, even Fanny and Edmund. Sir Thomas represents wisdom, authority, and an older, tried-and-true standard of behavior; as has already been noted, his return means Maria's marriage and Edmund's taking orders. While Edmund has done his best to protect the family from themselves, he is not the patriarch, and does not have his power or his authority.
Edmund's consultation with Fanny over his part in the play is both an attempt to seek legitimacy and a test of Fanny. Although Edmund knows that his reasoning is meager and will only include him in the common ruin, he is hoping to gain Fanny's approval. At the same time, he is also testing her reaction, curious to see how she will react to the news that he is to play opposite Mary and hoping that she will not agree with him just to appease him. This, of course, only increases Fanny's turmoil. Seeing Maria come so dangerously close to displaying her true emotions has been bad enough for Fanny; seeing Edmund do so nearly destroys her. Even so, Fanny is fascinated by the rehearsals and performances. Despite her aversion, she knows nearly all the parts by heart, and she admits that she gets an "innocent" enjoyment out of the proceedings. Fanny's enjoyment is not wholly innocent, though, for she is involved in most of the political intrigues among the cast. Again this shows how far-reaching the corruption of the "acting bug" is, but it also shows to what an extent "real life" is similar to a play acted on stage.