Edgar is dying. Linton continues to send appeals to his uncle to see Cathy. Edgar seems open to the idea of Cathy marrying Linton, for as Nelly reports: "Linton's letters bore few or no indications of his defective character" (27.4). Nelly doesn't tell him about Linton's health because she doesn't want to upset Edgar as he is dying.
Cathy and Nelly return to meet Linton at the same spot. Linton is extremely agitated. Cathy angrily questions his motives. (If you love me so much, why are you acting like such a freak?)
The truth comes out: if Linton doesn't get Cathy to marry him, Heathcliff will kill him. Obviously Linton is traitor.
Heathcliff arrives and insists that Cathy help get the withering boy back into the house. When Cathy maintains that Edgar has forbidden her to go to the Heights, Linton spills the beans that he himself cannot reenter the house without Cathy. So they all go into the house and Heathcliff locks the door and announces, "Had I been born where laws are less strict, and tastes less dainty, I should treat myself to a slow vivisection of those two, as an evening's amusement" (27.45). Wow. He has some seriously dark plans.
Cathy tries to fight for the key, but Heathcliff slaps her upside the head. He vows to be her father-in-law by morning.
Linton refuses to help Cathy and Nelly escape, as he is more interested in saving his own skin than in letting Cathy be with her father on his deathbed. Heathcliff adds that she came in of her own accord and that she is not going anywhere.
Nelly and Cathy spend a long sleepless night locked in a room, unable to escape through the narrow windows. In the morning, Heathcliff releases Cathy from the room but keeps Nelly there for four days and five nights.