In Emily Brontë's Wuthering Heights, Heathcliff is "adopted" when Mr. Earnshaw (Catherine and Hindley's father) finds the boy starving on the streets of Liverpool. Earnshaw and Heathcliff get along well, and Catherine is very fond of him, too. The two youngsters spend a great deal of time together growing up: while some people are frightened of the moors, Catherine and Heathcliff find comfort there, each enjoying the company of the other.
Hindley, though, is extremely jealous of Heathcliff and the attention he receives, and he is nasty. Hindley beats Heathcliff as a youngster and then Heathcliff holds it over Hindley's head, threatening to tell his father. It is an unhealthy relationship. Hindley goes away to school, and when Mr. Earnshaw dies, Hindley returns with a wife, and ownership of the Heights. From that moment on he makes Heathcliff's life miserable.
Early on, until Catherine is about twelve, she and Heathcliff have been devoted to each other. But Hindley's hand in—and control of— Heathcliff's life takes its toll.
Hindley's wife, at first thrilled with the Heights and Catherine, soon becomes peevish. She develops a strong dislike for Heathcliff. This is all it takes for Hindley to resume his torment Heathcliff. He makes Heathcliff work with the laborers, bans him from associating as one of the family, and he is no longer taught by the curate. When the Catherine and Heathcliff sneak off together, upon their return she is punished with extra lessons, while Heathcliff is whipped by Hindley. Every time they are caught, Heathcliff is beaten.
One afternoon, Catherine and Heathcliff go to spy through the windows at the neighboring home, Thrushcross Grange. While spying, the Earnshaw "children" think the Linton children are foolish and ridiculous in their behavior. Catherine is bitten by their dog. Though the Lintons are concerned for Catherine, they are very rude to Heathcliff. He leaves, but Catherine must stay while she recovers—for five weeks—and she grows to be friends with Edgar and Isabella. When finally able to come home, she is a very different young woman: she has manners, has been dressed in beautiful clothes, and been complimented excessively. She is more like the Lintons and much less like Heathcliff.
This is when the first Catherine disappears and the second one, who eventually marries Edgar Linton, appears. She has no time for Heathcliff. His rough manners and behavior embarrass her. While Hindley continues to abuse Heathcliff, he now has no support from Catherine—he begins to change as well.
Time passes and it seems that Catherine will marry Edgar. While she speaks to Nellie, the housekeeper about this, she states that Hindley has made it impossible for her to marry Heathcliff because of who he has become. Hearing only this part of the conversation, Heathcliff sneaks quietly away and leaves the Heights. What he does not hear is Catherine's confession, again, that she loves Heathcliff very much.
With Heathcliff gone, Catherine and Edgar marry—not that she is deeply in love with him. When Heathcliff returns, he is educated, and a man of means (money). His childhood friend has changed into a respectable young wife and their relationship is altered forever.
Heathcliff is visiting with Catherine one day when she is pregnant with her first child. She loses consciousness, gives birth and dies. Heathcliff is devastated, and damaged beyond repair as a person. What he might have been, he now will never be.