Bronte shows Heathcliff and Isabella’s relationship as one with a very unsound basis. Born out of Isabella’s infatuation, we know that their marriage is doomed from the start and it offers stark contrast with Heathcliff and Cathy’s relationship. You could argue that Bronte also utilises the relationship to challenge common beliefs held about marriage at the time: the brutality and destruction that evolves out of their union does not seem to fit the sensible, business-like attitude to which it is approached by Heathcliff in his bid to win the Grange. The dark, gothic spin that Bronte puts on this common situation shows the mental and physical effects of a marriage without love.
In the early stages of the book when we fist see Heathcliff and Isabella together, we do not suspect how their relationship will evolve. Arguably, though, things do not really change between how the pair feel about each other through the novel- true, things do waver a bit when Heathcliff returns but the feelings that develop there are both one-sided and short lived. Furthermore, to Heathcliff, Isabella seems to remain as little more than “Edgar’s sister” even when they are husband and wife. The benefits in Heathcliff marrying Isabella are not merely financial, she also offers a means by which to wound Edgar and to interpose himself further into his thoughts and his marriage with Cathy. In this sense, Heathcliff’s feelings towards Isabella have not gone much beyond his attitude at their first meeting- their marriage has more to do with Heathcliff and Edgar than it has with Isabella as an individual. To Heathcliff, she remains as nothing more than “Edgar’s sister”, a tool for him to cause destruction and for his own financial benefit. However, in Isabella being taken away from the Grange, Heathcliff has involuntarily made life better for Cathy and Edgar by remaining out of the picture himself so perhaps their marriage is also a tool for Bronte to change the atmosphere at the Heights before the build up to Cathy’s death- the calm before the storm.
Heathcliff and Isabella’s relationship somewhat mirrors that of Cathy and Edgar. Both Cathy and Heathcliff marry, at least to some extent, for selfish reasons. However, while Cathy’s choice would have been received as a sensible decision, Heathcliff’s is blown up to such a monstrous scale that a
Victorian audience would have been forced into admitting that there is something fundamentally wrong with relationships based on false love and the promise of land and profit. Although Cathy does have fond feelings for Edgar, she admits to Nelly that the qualities in him she finds the most attractive are that he is “handsome and rich”. She is less cruel to her husband than Heathcliff is to his partner but their actions are still very similar in their exploitation of the Lintons. This forces the reader to draw comparisons between the two couples who have both acted lawfully. Perhaps Bronte is condemning common attitudes towards marriage and Cathy and Edgar offer an insight that the reader can understand. In some ways, Heathcliff and Isabella are merely an extension of this relationship, building further on the flaws to a marriage with a loveless basis and offer a drastic example of the horror that can be created in a lawful and supposedly practical situation.
Isabella and Heathcliff’s relationship also works to challenge misconceptions about “good” behaviour. Isabella’s brief infatuation and her intense unhappiness following her marriage encourages aspects of brutality in her personality. Rather like with the dog when she was a little girl, Isabella’s initial want for Heathcliff made her savage, as Heathcliff himself put it, “no brutality disgusted her”. The word “disgusted” portrays the reaction that Heathcliff had perhaps been expecting as something involuntary, something that you find deeply disturbing despite any efforts. The lack of any such reaction shows that, to any surprise, Isabella feels comfortable in such a disturbing situation. This ruthless side to her is reinforced in later chapters with her relentless mockery after Cathy’s death. This lack of remorse is indistinguishable against Heathcliff’s savagery and we are forced to admit this when both are under the same roof. Bronte therefore portrays none of her characters as completely pure and we can see both light and dark in all of them. The difference lies in how surprised readers would be in uncovering the darkness in characters that they had earlier deemed as respectable. Their marriage, therefore, challenges the idea that only characters of low status contain such brutality as we can see massive similarities in Heathcliff and Isabella’s temperaments.
Overall, I would say that Bronte presents Heathcliff and Isabella’s relationship as completely destructive. It offers no happiness and shows us the danger of trusting someone in such a context without any basis to do so. It is also a platform from which we can contrast to other relationships and see the differences and, more importantly, the similarities in them.