Cathy is growing up a favorite of her father. She is not allowed to leave the grounds of Thrushcross Grange and has no notion of Heathcliff or Wuthering Heights. However, like her mother, she yearns to explore the moors and a certain rock formation called Penistone Crags. Because you have to go past the Heights to get there, Edgar forbids it.
Isabella has moved to London and had a son, Linton Heathcliff, who is now twelve. Dying, Isabella persuades Edgar to come to bid her farewell and take her child.
When Edgar leaves, Nelly is left alone to watch after young Cathy. She allows Cathy to ramble around the Grange playing games, but she always keeps the gates locked. Sure enough, one day Cathy takes off and goes straight up to Wuthering Heights.
Nelly goes off to the Heights in search of Cathy, and finds the girl happily chatting with the shy, awkward Hareton. As it turns out Heathcliff is not at home.
Angry at Cathy, Nelly tries to make the girl go home right away, but Cathy resists leaving the Heights. She thinks it's Hareton's house, but when she finds out it isn't, Cathy starts treating him like a servant. She's shocked when he starts cussing her out.
Nelly angrily tells Cathy that the rude and rough young man she thought was a servant is her cousin, Hareton. Cathy refuses to accept that and insists that her father is going to London to get her cousin (Linton Heathcliff). Apparently she doesn't know you can have more than one cousin.
Nelly observes the young man that Hareton has become—"a well-made, athletic youth, good-looking in features, and stout and healthy" (18.78). Heathcliff has denied him any education, so between his uncle and Joseph he has grown up without manners or guidance of any sort.
Nelly tells Cathy that her father would be very unhappy if he heard she was at the Heights.