Catherine and Heathcliff had often made fun of the Lintons when they were younger. This is what they are doing when Catherine is bitten by their dog and must stay and recuperate at Thrushcross Grange. At this time, she meets Edgar Linton and he falls in love with her. They eventually marry. Heathcliff returns and finds Catherine married to Edgar. Edgar's sister Isabella becomes infatuated with Heathcliff because he is grown up, handsome and rich. Heathcliff plans to take advantage of this, marry Isabella, get her inheritance and also get back at Catherine. Catherine tells Heathcliff that he could not possibly marry a Linton, which is strange because she has done the same thing. Catherine knows that Heathcliff does not really love Isabella. Plus, she wants Heathcliff for herself, even though she is married to Edgar. She has also become fond of Isabella who is now her sister-in-law and she knows that Isabella is a flighty woman with not much sense, so she does not approve of the marriage for Isabella or Heathcliff. It is partly from selfishness and partly from concern for Isabella that Catherine does not approve of their marriage.