She was much too fond of Heathcliff. The greatest punishment we could invent for her was to keep her separate from him: yet she got chided more than any of us on his account. (5.10)
For Catherine and Heathcliff, love and punishment will always intermingle. Theirs is a tormented love that would probably not do well under peaceful circumstances. They seem to thrive on drama.
The soft thing looked askance through the window: he possessed the power to depart as much as a cat possesses the power to leave a mouse half killed, or a bird half eaten. Ah, I thought, there will be no saving him: he's doomed, and flies to his fate! . . . I saw the quarrel had merely effected a closer intimacy—had broken the outworks of youthful timidity, and enabled them to forsake the disguise of friendship, and confess themselves lovers. (8.87)
With Edgar and Catherine—as with most relationships in Wuthering Heights—violence and desire go hand-in-hand. Edgar is so taken with Catherine that he refuses to heed the warnings of her troubled behavior. In this sense, he shares one thing with Heathcliff: a masochistic attraction to drama.
My love for Linton is like the foliage in the woods: time will change it, I'm well aware, as winter changes the trees. My love for Heathcliff resembles the eternal rocks beneath: a source of little visible delight, but necessary. Nelly, I am Heathcliff! He's always, always in my mind: not as a pleasure, any more than I am always a pleasure to myself, but as my own being. So don't talk of our separation again: it is impracticable. (9.101)
To Catherine, she and Heathcliff are one and the same; thus marriage to Edgar does not mean leaving the man she really loves. That Heathcliff sees her marriage as a betrayal is what ultimately divides them.
It would degrade me to marry Heathcliff now; so he shall never know how I love him: and that, not because he's handsome, Nelly, but because he's more myself than I am. Whatever our souls are made of, his and mine are the same; and Linton's is as different as a moonbeam from lightning, or frost from fire. (9.92)
Though she loves him as her own being, Catherine sees Heathcliff as beneath her compared to the social promise of marriage to Edgar. It's hard to reconcile such profound love with the choice she makes, but somehow she manages to work out the logic in her head.
His new source of trouble sprang from the not anticipated misfortune of Isabella Linton evincing a sudden and irresistible attraction towards the tolerated guest. (10.82)
Isabella's love for Heathcliff is one of Edgar's biggest nightmares. As children, he and Isabella had mocked Heathcliff together. Edgar still treats the adopted Heathcliff as one of the servant class.
Catherine Linton Heathcliff
"Oh, I will die," she exclaimed, "since no one cares anything about me. I wish I had not taken that." Then a good while after I heard her murmur, "No, I'll not die—he'd be glad—he does not love me at all—he would never miss me!" (12.6)
Catherine enjoys engineering the romantic dramas in her life. She yearns to provoke Edgar into a frenzy of concern, but he will never be as tormented as she would like.
"We've braved its ghosts often together, and dared each other to stand among the graves and ask them to come. But, Heathcliff, if I dare you now, will you venture? If you do, I'll keep you. I'll not lie there by myself: they may bury me twelve feet deep, and throw the church down over me, but I won't rest till you are with me. I never will!" (12.52)
Not even the divide between life and death will keep Catherine and Heathcliff apart. Had he heard her say these words, he would have been comforted. Being haunted by her is his greatest wish after she dies.
Two words would comprehend my future—death and hell: existence, after losing her, would be hell. Yet I was a fool to fancy for a moment that she valued Edgar Linton's attachment more than mine. If he loved with all the powers of his puny being, he couldn't love as much in eighty years as I could in a day. (14.23)
Life without Catherine is not worth living. The only emotion that begins to compensate for Heathcliff's loss is bitterness. Despite her unfortunate choice for a husband, Heathcliff knows that Edgar is incapable of loving her the way he does.
"Are you possessed with a devil," he pursued, savagely, "to talk in that manner to me when you are dying? Do you reflect that all those words will be branded in my memory, and eating deeper eternally after you have left me? You know you lie to say I have killed you: and, Catherine, you know that I could as soon forget you as my existence!" (15.25)
Catherine torments Heathcliff until he day she dies—and beyond. Importantly, this moment is the only time that Heathcliff confronts Catherine on her behavior.
Ellen "Nelly" Dean
"'Loving!' cried I, as scornfully as I could utter the word. 'Loving!' Did anybody ever hear the like! I might just as well talk of loving the miller who comes once a year to buy our corn. Pretty loving, indeed! and both times together you have seen Linton hardly four hours in your life! Now here is the babyish trash. I'm going with it to the library; and we'll see what your father says to such loving." (21.140)
Nelly Dean tries to knock some sense into Cathy regarding her affair with Linton Heathcliff. It's interesting to note how gutsy Nelly is in the way she talks to Cathy. After all, Nelly is a housekeeper and Cathy is the master's daughter.
The intimacy thus commenced grew rapidly; though it encountered temporary interruptions. Earnshaw was not to be civilized with a wish; and my young lady was no philosopher, and no paragon of patience; but both their minds tending to the same point—one loving and desiring to esteem, and the other loving and desiring to be esteemed—they contrived in the end to reach it. (32.110)
With all the reasons in the world to dislike each other, Cathy and Hareton still fall in love. Their mutual sympathy changes the tone of the novel and allows for something of a happy ending.
"Come in! come in!" he sobbed. "Cathy, do come. Oh, do—once more! Oh! My heart's darling, hear me this time—Catherine, at last!" (3.83)
Just a glimpse of Catherine would assuage the long-suffering Heathcliff, who believes in communication beyond the grave. He is far from afraid of ghosts and has clearly spent a lot of time trying to get Catherine to haunt him.