Quite a few things happen to Holden after he spends the afternoon in the park. In fact, one could say that his behavior becomes very erratic after he meets up with Sally, perhaps more so than usual. First, he decides during his date with her that he would like to marry her, and they fight when she seems less than enthusiastic about the prospect, which ends in Holden leaving. He decides to meet up with an older friend, Carl Luce, and they drink at Wicker Bar later that night after Holden sees a movie by himself. Holden gets pretty drunk there, and begins to grill Carl about his sex life, to which Carl responds unfavorably, reminding Holden that he had told him to see his dad, who is a psychiatrist.
After that, Holden drunkenly wanders around, later breaking into his house to see Phoebe, his little sister. He realizes that he has no place to sleep, so he calls up an old English teacher, who lectures him before putting him to bed on the couch. Later, he becomes freaked out when he wakes up to find the teacher petting him on the head. He leaves, and spends the entire rest of the morning walking around, fearing that he will disappear if he steps off of the curb. He may be having a psychotic episode at this point.
Eventually, he decides to run away and tells Phoebe so in a note that he leaves for her. She meets him at the museum later with her suitcase, and pleads for him to take her with him. They argue over it, but make up and decide to go to the zoo together. He watches Phoebe ride the carousel twice, in the rain, and decides that he is happy. After that, he simply goes home, and the book ends with him taking therapy and feeling like he misses everyone.