A suspicious Nelly finds out that Cathy has been sneaking away to the Heights during her illness. Nelly forces the truth out of her, and Cathy briefly takes over the narrative.
Here's Cathy's story: she goes to the Heights every night while Nelly is sick. She and Linton spend all sorts of time talking and telling stories, finding out how little in common they have.
One day, she runs into Hareton, who tries to impress her with the fact that he can now read his own name above the door. She just mocks him and goes into the house. Hareton bursts in and throws a screaming Linton into the kitchen.
Linton later blames Cathy for the scene, but they make up. And that's the end of Cathy's narration.
Nelly promptly tells Edgar about Cathy's visits to the Heights; again, she is forbidden to go there.