Not long afterward, Nelly stops by Wuthering Heights as she is walking past on some other errand and encounters her former charge, Hareton, who curses and throws stones at her. Hareton tells her that it was Heathcliff who taught him to curse, and that Heathcliff also refused to allow Hareton to be educated. Heathcliff then appears, and Nelly flees.
Heathcliff's revenge on Hindley includes doing to Hareton what Hindley did to him. As result, Hareton has become a kind of mirror image of Heathcliff as a boy—a wild child too ignorant even to know what has been taken from him.
The following day, Nelly and Catherine observe Heathcliff and Isabella embracing in the Grange's garden. Catherine confronts Heathcliff in the kitchen about his feelings for Isabella. She offers to convince Edgar to allow the marriage if Heathcliff truly loves Isabella. But Heathcliff answers that Catherine wronged him when she married Edgar, and that he plans to get revenge.
Heathcliff, as a natural man, is concerned with what is right or wrong, not with how things appear. But once wronged, he becomes completely consumed by the need for revenge, and is willing to trample or hurt anyone (perhaps with the exception of Catherine) to get it.
Informed of the confrontation by Nelly, Edgar rushes in and orders Heathcliff to leave. Heathcliff refuses. Edgar moves to get the servants to come and help him remove Heathcliff, but Catherine forces Edgar to confront Heathcliff alone by locking the door into the house and throwing the key in the fire. Edgar at first hides his face, but Catherine taunts him and he punches the larger Heathcliff in the neck. Then he runs from the kitchen into the garden to get the servants. Deciding he can't fight off Edgar and a bunch of armed servants, Heathcliff leaves.
The passionate Catherine wants the civilized Edgar to be more macho. She wants him to be more like the wild and passionate Heathcliff. Edgar's attempt to comply, after she forces him into it, is pitiful..
Once Heathcliff is gone, Edgar furiously demands that Catherine choose between him and Heathcliff. Catherine refuses to talk to him, and retreats to her room, where she stays for three days without eating. In the meantime, Edgar, distraught, tells Isabella to either stay away from Heathcliff or be disowned.
Like Heathcliff, Catherine is prone to wild, reckless actions that the civilized Edgar can't understand. Note also how Edgar treats Isabella for following her heart, when he did the same when he married Catherine.