That night little Catherine is born, two months premature, and her mother dies in childbirth. Edgar begins mourning. On top of the whole mess, he has no heir (girls don't count).
Nelly goes out to the garden to break the news to Heathcliff, but he already knows. Still, he begs for all of the grisly details and, of course, wants to know if she mentioned him.
Heathcliff doesn't want Catherine to rest in peace. He cannot live without her, and he cries out for her to haunt him.
Heathcliff sneaks into the house to say one final goodbye to Catherine in her coffin. As a parting gesture, he replaces Edgar's hair in the locket around her neck with a lock of his own.
Instead of being buried in a chapel or with the Linton family, Catherine's body is laid to rest outside, near the moor and peat mould (decomposed vegetable matter that covers uncultivated land—the "mould" part is because it is saturated with water).