The day after the party, Marianne is awake early writing a last letter to Willoughby. She through her sobs writes him, asking him to explain his behavior towards her the previous evening. She receives a reply, which lets her know he never meant to lead her on. He explains he only had friendly affection for her and her family, in fact he is engaged to another woman and hopes to be married soon. This letter throws Marianne into fresh spasms of grief and she refuses Elinor's attempts to comfort her.

Elinor is able to read not only Willoughby's letter to Marianne, but also Marianne's letters to him and she is surprised that her sister would write such inappropriate letters. Marianne is very forward in letting her feelings be known to Willoughby, which is not correct conduct for a single lady in the 1800's.

Marianne tells Elinor she and Willoughby are not engaged and he has never told her he loves her. Marianne thought he loved her and wanted to marry her, because of how he spoke to her and treated her. Elinor tries to urge her sister to compose herself and carry on with some dignity, but Marianne refuses to do anything but express her grief. She blames the world and the other girl for her misfortune, but later realizes Willoughby is at fault also, for leading her on. She now wants to leave London as soon as possible.

Mrs. Jennings on returning from her morning errands, tells Elinor she has been told of Willoughby's engagement to Miss Grey. It seems Miss Grey is an orphan and has inherited fifty thousand pounds, making her a rich woman. She is under the guardianship of Mr. and Mrs. Ellison, who are happy to have her married off, as she and Mrs. Ellison do not get along well.

Mrs. Jennings tries to comfort Marianne by giving into her every whim, but Marianne is still inconsolable. She has arranged for a few people to come to dinner that evening and hopes Colonel Brandon will visit the house. He does come for tea, but Marianne is in bed by that time. He seems relieved to not have to interact with her, instead he talks to Elinor about the situation. Mrs. Jennings believes the news will make the colonel happy, but instead he remains serious and contemplative throughout the evening.

The next morning Colonel Brandon visits Elinor at Mrs. Jennings's home. He has information about Willoughby to tell her. He tells her about his first love, a young girl who was placed in the guardianship of his parents. He and the girl fell in love, but his father determined that she should marry his brother, so the colonel's family might have her money. The marriage was a disaster and the two were divorced, by this time the colonel was back in England after serving in the military. He found her in a sponging-house, a place where debtors are sentenced, and finds out she is dying. He took her out of there and made her comfortable until she died. She had a small daughter, which was from a romance she had after her marriage; the girl was placed in Colonel Brandon's care. He made sure she had schooling and then he placed her with a woman who took care of young ladies. The girl went with a friend to visit the friend's ailing father in Bath, there the girl met a man and disappeared. This all happened within the last year, he found her as she was about to give birth to the man's child. The man is John Willoughby, he does not take responsibility for the child or the mother.

Colonel Brandon is hoping this news will help Marianne see she is lucky to be away from Willoughby and how her circumstance could be much worse than it is. Elinor thanks Colonel Brandon for his information. She tells him she feels her sister will not suffer as she has been from her breakup, because the truth about Willoughby might help her realize he is not the man she thinks he is.

Though no one speaks to Marianne of Willoughby, everyone seems determined to speak of him to Elinor. The only one who is not constantly talking about him is Lady Middleton, which is a relief to Elinor.

Mrs. Dashwood after expressing her shock and sorrow about the ended relationship, decides the girls should stay five or six weeks with Mrs. Jennings. John Dashwood and his wife are returning to London in February and she wants the girls to visit with their brother.

In early February the news comes that Willoughby has married Miss Grey. Elinor tells her sister and Marianne begins to grieve for her lost relationship again. Elinor tries to motivate Marianne to go out, as she has not left the house since receiving the shocking news from Willoughby.

The Steele sisters come to London and Lucy takes great pleasure in reminding Elinor of her desire to leave London before February. Lucy thinks Elinor is staying on to see Edward at John Dashwood's home and try as she might, Elinor cannot convince her otherwise. The sisters both are bothersome to Elinor, as Anne insists in seeing Marianne, even though she has been told she cannot. Finally, Lucy manages to convince Anne to leave Marianne alone.

These chapters show how much misery Marianne feels, after being deceived by Willoughby. He is shown to be a man of no moral compass, who uses young women only for his own purposes. Elinor tries to help her sister cope with her situation, but Marianne seems to enjoy wallowing in her misery. Meanwhile, Colonel Brandon exposes his past and the ill effects Willoughby has had on the young woman under his guardianship.