Hindley returns for his father's funeral. He brings with him his somewhat silly and ineffectual wife, Frances. As his father's heir, Hindley is now master of Wuthering Heights and makes immediate changes, such as moving the servants to the back quarters. He also forces Heathcliff to give up his education and instead to work in the fields. Yet for the most part Hindley ignores both Heathcliff and Catherine, who escape their domineering brother by escaping to go play on the moors.
Hindley takes revenge on Heathcliff by using the rules of class (male inheritance) to assert dominance, and to use that dominance to deprive Heathcliff of an education and force him to work like a common laborer. Heathcliff, along with Catherine, find sanctuary from Hindley's vengefulness in nature.
One day, Heathcliff and Catherine don't return from one of their adventures and Hindley orders that they be locked out. Nelly, though, waits up for them, and she is there when Heathcliff comes back alone. He tells Nelly that he and Catherine had been at Thrushcross Grange, spying on Edgar and Isabella Linton. Heathcliff was impressed by their house, but he thought the Linton children were "idiots." When he and Catherine laughed aloud at them, the Lintons realized someone was outside. As Heathcliff and Catherine tried to escape, the Linton's dog, Skulker, caught them and bit Catherine's foot.
Heathcliff and Catherine, who embody nature, discover Edgar and Isabella, who are more civilized. And just as Heathcliff and Hareton laughed at Lockwood in chapter 2, Heathcliff and Catherine's first instinct is to laugh at the civilized Linton's for being weak and silly. Yet at the same time they are impressed by Thrushcross Grange itself. In other words, they are impressed by the trappings of civilization, by what being civilized can get you.
When the Lintons realized that Catherine is from Wuthering Heights, they bring her inside and insist that Catherine stay with them while she heals. But they are shocked at Heathcliff's rough clothes and language and refuse to let him stay with Catherine. Before leaving, Heathcliff spies on them: he sees how the Lintons fuss over Catherine, and how much she likes the attention.
By denying Heathcliff an education, Hindley forced Heathcliff into another, lower, class. And the civilized Lintons are very judgemental, and careful to keep out anyone of a lower class. Note also how Catherine has already learned that there are some pleasures to civilization.
The next day, Mr. Linton goes to Wuthering Heights and berates Hindley for letting Catherine run wild. Ashamed, Hindley blames Heathcliff and says that Heathcliff may no longer see or talk to Catherine.
Civilized people use shame as a weapon. And, ashamed, Hindley now takes further revenge on Heathcliff by trying to separate him from Catherine.