I got Miss Catherine and myself to Thrushcross Grange and, to my agreeable disappointment, she behaved infinitely better than I dared to expect. She seemed almost over-fond of Mr. Linton; and even his sister she showed plenty of affection…It was not the thorn bending to the honeysuckles but the honeysuckles embracing the thorn.

In Chapter 10, after marrying Edgar Linton, Catherine moves with Nelly Dean to Thrushcross Grange. Nelly observes that Catherine behaves better than she expected, “to her agreeable disappointment,” suggesting she secretly wants Catherine to behave badly. That Catherine does not behave badly somewhat contradicts Nelly’s notions of Catherine’s continued wildness, but it becomes clear she has not necessarily settled down. Though Catherine has affection for them, Nelly explains that Edgar and Isabella both yield to what she describes as Catherine’s domineering personality.

He took a seat opposite Catherine, who kept her gaze fixed on him as if she feared he would vanish were she to remove it. He did not raise his to her often: a quick glance now and then sufficed; but it flashed back, each time more confidently, the undisguised delight he drank from hers. . . . Not so Mr. Edgar: he grew pale with pure annoyance: a feeling that reached its climax when his lady rose, and stepping across the rug, seized Heathcliff’s hands again, and laughed like one beside herself.

Upon Heathcliff’s triumphant return in Chapter 10, Catherine is jubilant, and Edgar is less so. Having just referred to Heathcliff as a “runaway servant,” he appears uncomfortable in the face of his wife’s obvious closeness with a man he perceives to be far beneath them.

I wanted something to happen which might have the effect of freeing both Wuthering Heights and the Grange of Mr. Heathcliff, quietly . . . His visits were a continual nightmare to me; and I suspected, to my master also. His abode at the Heights was an oppression past explaining.

At the end of Chapter 10, Nelly explains that Heathcliff’s presence causes her immense disquiet. She hopes something will cause him to leave, because she fears he must be up to something nefarious.

Well, if I cannot keep Heathcliff as my friend—if Edgar will be mean and jealous, I’ll try to break their hearts by breaking my own. That will be a prompt way of finishing all, when I am pushed to extremity!

Toward the end of Chapter 11, following a confrontation between Heathcliff and Edgar that causes Edgar to issue her an ultimatum, Catherine vows to get revenge on them both by refusing to eat. She hopes the possibility of her death will drive them both to wild, frenzied action.

I engaged to carry a letter from him to my mistress; and should she consent, I promised to let him have intelligence of Linton’s next absence from home, when he might come . . . Was it right or wrong? I fear it was wrong, though expedient. I thought I prevented another explosion by compliance; and I thought, too, it might create a favourable crisis in Catherine’s mental illness[.]

In Chapter 14, Nelly Dean proves herself not merely a passive bystander. To deescalate the conflict when Heathcliff threatens to hold her hostage at Wuthering Heights, she agrees to not only bring Catherine a letter from Heathcliff but to let Heathcliff know when Edgar is away so that Heathcliff may visit the Grange. Nelly claims to Lockwood that she did so to prevent “another explosion” of Heathcliff’s temper, but she appears to have ulterior motives too. Catherine’s health is deteriorating, and the doctor has ordered her not to be disturbed, which Nelly knows full well. It’s possible she believes Heathcliff’s presence will improve Catherine’s health, but it’s equally possible, if not more so, that she is aware that such a “favourable crisis” will lead to her mistress’s death.