The next day, Goriot and Rastignac are getting ready to move out of the boardinghouse when Delphine arrives to see her father. Without them knowing, Rastignac eavesdrops on their conversation. Delphine is agitated because her husband has informed her that he has invested all of her dowry money and currently has nothing to return to her if she and her father continue with their lawsuit to reclaim her money. He wants her to wait several years, during which time he will come up with even more money, give her independence, and be a better husband. She has been moved by his request, and is unsure what to do. Goriot is angry and insistent that she is being tricked, but she explains that her husband is implicated in many shady business ventures and that they cannot try to get money out of him without risking her own name and reputation. Delphine persuades her father to let her manage her husband, but to review the relevant paperwork in a few days time.
At this point, they are interrupted by Anastasie, who is also in distress. She explains that her lover Maxime's debts were making him more and more desperate and she became afraid he was going to kill himself. She pawned her diamonds in order to pay Maxime's debt, but her husband found out. Restaud demanded that in exchange for not divorcing her and depriving her of her children, he wants signed access to all her money and property. Goriot is increasingly agitated at the disasters that have befallen his daughters, and is even more devastated to learn that Anastasie has still not successfully cleared all of the debts and wants more money. The two daughters quarrel, but Goriot succeeds in calming them. Rastignac bursts into the room and offers to assume the remaining debt himself, but Anastasie is mortified that he knows her secrets and storms out.
Goriot seems to have fallen ill, and after escorting Delphine home, Rastignac consults with Bianchon. Bianchon suspects Goriot is dying, but offers to do what he can.
Rastignac cannot help but be distracted by enjoying his new apartment with Delphine. She in turn is preoccupied with plans for the Beauseant ball: it stands to be a major social event because the Marquis d'Ajuda will be getting married to Miss Rochefide earlier that day, and Madame de Beauseant does not yet know. All of Paris wants to take ghoulish pleasure in her being forced to appear in public whilst heartbroken.
When Rastignac returns to the boarding house, Madame Vauquer is annoyed that he has not moved out, even though he has given notice. However, at this point, Goriot is too ill to be moved. He has also received another visit from Anastasie who got more money from him to cover the cost of her ballgown.
After a physician confirms that Goriot is dying, Rastignac goes to break the news to Delphine. She, however, is insistent on attending the ball. At the ball, Madame de Beauseant bears her grief nobly, and confides to Rastignac that she intends to leave Paris the following day and live quietly in the country.
When the ball ends very late that night, Rastignac returns to the boarding house and continues to nurse Goriot. His lack of money is becoming a problem, and Goriot continues to rave about his hopes that his daughters will come and see him. Frantic, Rastignac goes to the Restaud household and explains to the Comte that his father-in-law is dying, but the Comte is totally disinterested. Anastasie is also unwilling to disobey her husband and go to her father. Rastignac finds Delphine equally reluctant to go. He returns to the boarding house, where he and Bianchon have used their last money to try and make Goriot more comfortable. Goriot falls unconscious lamenting his love for his daughters, and Anastasie arrives after he has fallen unconscious. She remains by his side until he dies a few minutes later.
Rastignac and Bianchon make arrangements for a meagre funeral, and ask the Restaud and Nucingen families to contribute money. Neither sends anything and the funeral is attended by some of their household servants, but neither of the daughters attend. After the funeral, Rastignac stays at the cemetery, gazing out over Paris. He recommits to his goal of finding a place in Parisian society, and then goes to meet Delphine for dinner.
The hope of a promising future for Goriot, Rastignac, and Delphine is quickly extinguished due to Delphine not actually being emotionally committed to either man. When it starts to become clear that separating from her husband will have real financial and social consequences, she starts to waver on whether or not she wants to leave him. Delphine thinks she wants something, but as soon as she gets it, she proves fickle and wants something else. Once the novelty of her new apartment and her new lover wears off, she's disinterested in following through with the new life her father has worked so hard to create for her. Goriot's anguish and rage as he sees his plans start to collapse reflect how high his hopes had risen. He was on the verge of reclaiming Delphine and reestablishing a close relationship with her, but now it seems like she has been snatched back into a life he will be cut out of.
With Goriot losing control over Delphine, Anastasie also pushes him back into reacting to his daughters' whims rather than proactively helping them to make their lives better. Like various other female characters, Anastasie has fallen victim to her tenderness for her lover, and has now gotten herself into a desperate situation. If her husband divorces her, she will lose all her money, social position, and access to her children. Anastasie's position as a mother herself allows her to rationalize her manipulation of her father.
The Beauseant ball represents the culmination of Balzac's critique of Parisian high society. Madame de Beauseant's supposed friends and acquaintances take a voyeuristic pleasure in watching her suffer and be publicly embarrassed. Not only are all the individuals out to benefit themselves, they also take pleasure in the misfortune of others. The experience of the ball represents one of the final stages of Rastignac's education about the ways of the world. He is forced to accept that attending the ball is more important to Delphine than seeing her dying father, and he also watches Madame de Beauseant admit that she has been defeated by society. By this point, all of Rastignac's mentors seem defeated: Vautrin has been arrested, Madame de Beauseant is going into exile with a broken heart, and Goriot is now dying.
Despite his questionable actions, Rastignac shows genuine loyalty and integrity in faithfully nursing Goriot as he dies. Although he has no blood ties to the old man, Rastignac behaves more like a devoted child than Goriot's own daughters do. Goriot naively clings to the belief that his daughters are going to come to him until the very end, and even Rastignac cannot believe that Delphine and Anastasie are actually going to refuse to help their father. Balzac creates an even more tense effect by having Anastasie arrive while her father is still alive, but unconscious. Goriot dies effectively abandoned by the two women he gave everything to. The grim spectacle of his penniless funeral and the lack of anyone attending seems totally unjust given how Goriot has lived his life. With this scene, Balzac makes it clear that his vision of the world is an unjust one, in which kindness and generosity will not guarantee anything.
This grim and cynical conclusion makes the final image of Rastignac even more powerful. Rather than turning away from society in disgust, Rastignac is even more committed to finding a place for himself. He is also going to continue his relationship with Delphine, having seen how utterly heartless she has been. Rastignac has completed his maturation and education, and no longer has any illusions about human nature or the way the world works. Nonetheless, he still wants to obtain the power and privilege he has wanted all along.