Roquentin had moved to Bouville in order to study the Rollebon archives, so after abandoning his research he sees no reason to remain there. He plans to first visit his ex-lover Anny in Paris, return to Bouville to pack up his belongings, and then return to Paris indefinitely. He secretly hopes that he can both explain his Nausea to Anny and that they can get back together. As he waits for his train he feels ready for an adventure.
He and Anny meet as planned, but they are very awkward around each other. Roquentin is disappointed to find that Anny has grown old and is no longer as attractive as he remembered. He is also surprised that she is the mistress of a number of men who pay for her apartment. Roquentin can never completely understand what Anny is talking about, as she intermittently laughs at his awkwardness. She says that she is very happy to see him because he never changes. She calls him her milestone, claiming that she needs him to remain the same so she can tell how much she has changed over the years.
Their conversation turns to their past relationship. Roquentin can remember very little of the things they did together, feeling overwhelmed by Anny's precise memory. Anny is obsessed with the past: she remembers entire passages from plays and constantly studies French history. She also speaks of "perfect moments," which she describes as past events whose importance she embraced while they were happening. But she thinks that they no longer exist; she can't recreate emotions that are in the past. Roquentin suspects that she has come to similar conclusions as him about the nature of time and existence. He describes his Nausea and discovery that existence precedes essence, but Anny doesn't agree with him at all. She asks him to leave and he reluctantly obeys.
Back in Bouville, Roquentin prepares to return to Paris for good. He is sad that he and Anny cannot be together but a part of him had expected nothing to come of their meeting. He feels very lonely, especially while walking around the city streets, but takes comfort from his awareness of existence. He wants to say goodbye to the Self-Taught Man, but sees him fondling a small boy in public. Other people see the offence and chase the Self-Taught Man away. Left to himself, Roquentin goes back to his old cafe one last time and asks to hear his favorite record, "Some of these days." As he listens to the song over and over again, he resolves to write a novel that will have nothing to do with the question of existence. He thinks that it might clarify who he was in the past and prevent him from remembering his life with disgust.
Sartre uses this final section to demonstrate the inability to justify one's existence through the existence of another person. Roquentin first realizes this after discovering the futility of "resurrecting" the Marquis de Rollebon. Anny questions her essence and existence just as Roquentin does, but rather than embrace her existential freedom by creating her own essence in the present, she relies on Roquentin to define herself. For instance, she calls him her "milestone," exclaiming that she wants him to stay the same so she can "measure" her own changes. This is an example of what Sartre called "bad faith." Anny has the freedom to create her own essence, meaning that she can define who she is without adhering to any external standards. Instead, she relies own Roquentin to create her essence, just as Roquentin had previously relied on the Marquis de Rollebon.
Roquentin's conversation with Anny also emphasizes the failure of the past to provide a justification for one's existence. For Roquentin, Anny is a part of his nonexistent past that, no matter how hard he tries, no longer has any meaning. He can't even remember things about himself that Anny remembers with ease. As a result, he is free to live in the present, unconstrained by things he has done in the past. But Anny declares that she "lives in the past." She reads Jules Michelet's History of France over and over again, while attempting to remember everything with minute accuracy so she can relive "perfect moments" whenever she chooses. Sartre thus uses the Antoine/Anny duality to show how a reliance on the past prevents one from being free. By making Roquentin her "milestone," Anny tries to live in the past by pretending that time has had no effect on him. Her unwillingness to take action because she feared "fatal results" is thus a symptom of her not being able to handle the responsibility of being free. As Roquentin says later understands, she is a "dead woman."