Because Don has talked to several mental health professionals—a detail he has never revealed up to this point—he has an efficient way of telling his life story. His father owns a hardware store; his younger brother, who lives at home, will eventually inherit it. His mother is kind, but Don finds her smothering. He reiterates that his sister Michelle died when she was 40 years old and then shares that his mother was devastated by the loss. Don says he was also affected by her death. He is not close to anyone in his family since his sister died, as he and his father do not share an emotional connection and his brother felt competitive over their father’s affection. 

On the school front, which Don has also mentioned beforehand, he loved science and lacked friends. He also reveals that he excelled in English. Don was originally a computer science major until his 21st birthday. Don ends his story saying that there is no history of mental disorders in his family, but he privately reflects on the appointments he’s had in the past. Several psychiatrists and psychologists attributed Don’s behavior and mannerisms to disorders like obsessive-compulsive disorder, depression, and even schizophrenia. Don believes these are misdiagnoses and that his brain is simply “wired” differently than the neurotypical person. He wonders if the children with Asperger’s he met during the lecture in Chapter 1 might have to suffer through similar experiences.

Rosie asks what happened on his 21st birthday to instigate switching majors. He reveals that, at the party his mother threw for him, his uncle performed an overly enthusiastic (i.e., extremely hurtful) roast. He humiliated Don with highly personal stories about how much pain and embarrassment he caused his family. As a result, Don changed his major from computer science to genetics, determined not to fulfill the role of the stereotypical computer geek.

Rosie then wants to know more about Don’s father, as she assumes part of the reason Don acts the way he does is because he lacked a strong relationship with his dad. She admits that she probably feels that way because of her own dysfunctional relationship with Phil and her lack of a relationship with her biological father. However, when Don asks her to elaborate by telling her own life story, Rosie deflects. While she goes to the bathroom, Don reviews two packages he received before the trip, one from Gene and one from Claudia. The former gave him a book on sex; the latter gave him a change of clothes. Upon her return, Rosie spends the rest of the trip to Los Angeles sleeping or watching movies so she can decompress.

They arrive in New York after the flight from Los Angeles, and Rosie is desperate for a cigarette because she hadn’t had one in 18 and a half hours. The pair decide that Don will need a cover story when they visit the Eslers: He decides to be a hardware store owner named Austin. Rosie wants to go to the hotel to change, but Don says they must go to a shop first. He takes them to the Hermes shop, so he can buy Claudia an expensive scarf for her upcoming birthday. Though he allotted only four minutes for this, they end up spending an hour as Rosie convinces Don to consider nearly every scarf in the store. However, Don enjoyed the time because he had never considered how attention to aesthetic detail factored into buying clothes.

As Don is dressed in attire suited for travel, Rosie convinces him to change into the clothes Claudia gave him. The pair arrive 45 minutes late for dinner with the Eslers, which seems to go successfully, especially when Don manages to get the DNA sample. However, after dinner, Isaac asks him to repair a leaky faucet in the basement. As they go downstairs, the lights go out, and Isaac asks Don if he’s OK—calling him by his real name. When Don responds instinctually, Isaac reveals he has known who Don is the entire time; the unsolicited correspondence from Don’s university caused him to look into who exactly was sending them. He also tells Don that he knows the answer to Rosie’s paternity question but promised to never reveal the answer; he warns Don to consider drop the issue entirely.

Rosie and Don sleep in separate rooms that night. The next day, Don has already decided not to tell Rosie about his conversation with Isaac or that he saw a photo from Isaac and his wife’s wedding that shows Geoffrey Case as the best man. 

As promised, Rosie takes over their schedule, refusing any of Don’s protestations. When he tries to assert his typical routine of eating before showering, she says, “You’re like an old man—I always have my breakfast before I shower, don’t sit in my chair, that’s where I sit” (204). Then, she insists that he put on the shirt and jeans Claudia gave him for the trip because she won’t be seen with him dressed like a “bum” (204).

Don forces himself to go along with whatever Rosie has planned for the next two days, after telling himself that the best times of his life, with the exception of his visits to the Museum of Natural History, have all been with Rosie. He is also taken aback by her accusation of him being an old man, realizing that she is right; he and his father have special chairs.

Don has a wonderful day with Rosie, eating breakfast, shopping for new clothes, and eating ice cream. With the latter, Don panics that he is about to relive the Apricot Ice Cream Disaster. Rosie, of course, refutes his belief that all ice cream tastes the same, but instead of being offended the way Elizabeth was, she bets him that she would be able to identify two different ice cream flavors without looking. Don picks apricot and mango, and she correctly guesses each time. She hands him the apricot ice cream afterward, positing that sharing ice cream is no different than kissing someone. He is thrilled, though he maintains it’s irrational, that Rosie could be implying she wants to kiss him.

That evening, they see Spider-Man on Broadway, per the parameters of the ice cream bet, then eat dinner at Momofuku Ko. While there, Don has a conversation with another patron but feels he is reverting to his usual mannerisms when interacting with others. Sensing Don’s awkwardness, however, the man says that the best thing about New York City is that it allows everyone to fit in. At the end of the meal, Don tells Rosie this is the best day of his adult life.