The missing cat search
When Toru goes to find the missing house cat (who is ironically named) he discovers a young pixie-ish girl who leads him to an abandoned house. He sees lots of cats, but no Noboru.
The affair
The cat isn't the only one who's missing. Toru soon finds out his wife is leaving him for her boyfriend, with whom she is deeply satisfied. He didn't even know she was dating anyone. He only got his first clue when he noticed that another man must've bought her a perfume. Before he can confront her, she nips it in the bud.
Creta Kano's story
The missing cat shares a name with Noboru, Creta Kano's rapist. When Toru thinks he is going to learn about the location of Noboru, the cat, he is faced with the evil Noboru, the person.
Nutmeg and the prostitution service
When Toru meets Nutmeg, he becomes fascinated by her and chooses to work for her as a sexual servant for her elderly clients. The irony is that it's really his wife, and he's being put under a spell that makes him misunderstand reality.
The murder
Almost randomly, Kumiko reappears to the narrative and chooses to murder her brother who raped Creta. She does so after Toru makes much the same decision about him in one of his spell-bound fantasies. The murder is accomplished when Kumiko unplugs the machinery keeping Noboru alive.