Catherine's brain fever worsens, but under Edgar's close care, she recovers. Well, almost. She's pregnant.
In the meantime, Isabella has sent a letter to Edgar announcing her marriage to Heathcliff. He doesn't reply.
Two weeks later, she writes to Nelly announcing that she is living up at the Heights. She also has a few choice words about her new residence and her spouse.
Isabella briefly takes over the narrative, as she tells Nelly in the letter that she basically thinks Heathcliff is the devil. The house is a pigsty and Hareton is a little hooligan. Joseph is still a ranting, cursing crank and Hindley is a ghost of his former self, having been worn down by his own issues and the vengeful abuse of his roommate/semi-brother Heathcliff. It's a real ragtag gang—not the kind of company Isabella is used to keeping.
Isabella already misses the Grange and realizes she will have no allies at the Heights. On top of all of that, there are no servants to show her to her "chamber" and treat her in the way she is accustomed.
Hindley shows Isabella his gun and warns her to lock her bedroom door because he is planning to murder Heathcliff. Hindley's confessions reveal that he has lost a heap of money and is now in Heathcliff's debt. Heathcliff would kill him or kick him out, but he wants his money back.
Isabella spends the night sleeping in a chair in Hareton's room. Heathcliff comes looking for her in the middle of the night. He tells her Catherine is sick and that it is her brother's fault. Heathcliff also tells her that until he can get to Edgar, he will make Isabella suffer in his place.
She closes the letter, and her narration, by begging Nelly to send help.