Just a few days after the funeral, Isabella comes to Thrushcross Grange at a time when she knows Edgar will be asleep in his room. Disheveled and laughing hysterically, Isabella tells Nelly, who is taking care of the baby Cathy, that she knows Edgar won't allow her to stay, but that she needs Nelly's help.
Isabella's poor treatment at the hands of Heathcliff have clearly unhinged her. Yet she also has the presence of mind to know that Edgar, always conscience of propriety, will never forgive her for running off with Heathcliff.
Isabella tells Nelly that Hindley desperately tried to stay sober in order to attend Catherine's funeral, but fell apart the morning of the funeral and started drinking. Then, while Heathcliff was out standing vigil at Catherine's grave, Hindley locked the doors of Wuthering Heights to keep Heathcliff out and told Isabella that he planned to shoot Heathcliff.
Note how Hindley's plan mirrors what he did when Heathcliff and Catherine, as children, were later to return in chapter 6. It is as if the characters are endlessly repeating the same pattern as they seek revenge on each other.
When Heathcliff returned, Isabella warned him of Hindley's plans, but didn't let him into the house. Hindley then tried to shoot Heathcliff from a first floor window, but Heathcliff wrenched away the end of the gun and in the process wounded Hindley in the wrist with the blade of the gun's bayonet. Heathcliff then broke into the house through that window and beat Hindley. The next morning, Hindley did not remember what happened, but Isabella reminded him. The two men once again fell to fighting, at which point Isabella ran to Thrushcross Grange.
The endless back and forth of revenge and recrimination continues.
Nelly then jumps a bit ahead in her story to say that after leaving Thrushcross Grange, Isabella went to live near London, where she gave birth to a sickly boy, whom she named Linton. Heathcliff eventually learned where Isabella and his son were, but did not go after them. Isabella died when Linton was twelve.
As a male heir to Isabella, the birth of Linton solidifies Heathcliff's claim on Thrushcross Grange into the next generation.
Hindley dies six months after Catherine, and Nelly goes to Wuthering Heights to look after the funeral and to bring Hareton back to the Grange. But Nelly is shocked to learn that Hindley died deeply in debt to Heathcliff, who now owns Wuthering Heights. In addition, Heathcliff refuses to let Hareton leave Wuthering Heights, and implies that he eventually plans to bring Linton to Wuthering Heights as well.
Heathcliff's revenge against Hindley is complete with the combination of Hindley's death and ownership of Wuthering Heights passing into Heathcliff's hands. Yet as his continued oppression of Hareton shows, and interest in Linton implies, his plans are far from finished.
Nelly then adds that Hareton, who should be the master of Wuthering Heights, now is forced to live as a dependant and servant to Heathcliff.
Though born into a family of high class, Hareton has had his position stolen from him.