For two months after Isabella and Heathcliff flee, Catherine remains gravely ill with what is called a brain fever. Edgar nurses Catherine with total devotion, though Dr. Kenneth warns that Catherine may survive only as a permanent source of anxiety. When Catherine is finally declared out of danger, Edgar hopes both Catherine's body and mind will recover.

At the beginning of March, Catherine leaves her room for the first time. Edgar gives Catherine early crocuses, which make Catherine think of Wuthering Heights and the thawing moors, but Catherine also speaks as if she will return there only once more, permanently. Because the sickroom worsens Catherine's despondency, Edgar and Nelly move Catherine downstairs to the parlour and then to a room on the same floor; Nelly also reveals that Catherine's life now matters doubly because Catherine is pregnant, raising hope for an heir to Edgar's estate.

Nelly then recounts Isabella's communications after the elopement. Isabella first sends Edgar a brief note announcing her marriage to Heathcliff and asking for remembrance and reconciliation, but Edgar does not answer. Two weeks later, Isabella writes a long letter to Nelly from Wuthering Heights, begging Nelly to visit and asking whether Heathcliff is a man, a madman, or a devil.

In Isabella's letter, Isabella describes arriving at Wuthering Heights after Heathcliff pauses on the moors to look toward Thrushcross Grange. Joseph receives Isabella with contempt, Hareton behaves like a savage child and threatens Isabella with the bulldog Throttler, and Hindley appears gaunt, hostile, and half-mad. Isabella realizes that no one at Wuthering Heights will protect Isabella from Heathcliff, and Hindley confirms the danger by showing Isabella a pistol fitted with a knife, saying he tries Heathcliff's door every night and will kill Heathcliff if he finds it open.

Isabella tries to make herself useful by preparing porridge, but Joseph mocks Isabella, Hareton dirties the milk, and Isabella cannot secure a proper room. Joseph shows Isabella filthy or unsuitable rooms, explains that Heathcliff's chamber is locked, and finally leaves Isabella in distress after Isabella throws down the supper tray. Isabella cleans up with the help of Throttler and eventually finds shelter in Hareton's room, where Isabella falls asleep.

Heathcliff wakes Isabella and is enraged when Isabella refers to the locked chamber as their room. Heathcliff makes clear that Isabella has no place or claim there, tells Isabella about Catherine's illness, blames Edgar for it, and promises that Isabella will suffer in Edgar's place until Heathcliff can reach Edgar. Isabella ends the letter declaring hatred for Heathcliff, admitting her misery and folly, and begging Nelly to come without telling anyone at Thrushcross Grange.