So, it appears that Catherine II is falling in love.
The catch to this is that she is falling in love with Linton. This poses some issues, as he is 1) Her cousin 2)Heathcliff's son and 3) He is dying.
So Ellen falls sick, and Edgar is already kind of sick. Edgar fell sick a few chapters back of a cold, but it appears that he isn't going to get better any time soon. Catherine II makes the most of this, and whilst they are sleeping, she steals out and meets up with her forbidden lover Linton. He is also becoming increasingly ill.
Ellen is back to normalcy within three weeks, and discovers that Catherine II had been stealing out of the Grange to go and meet with Linton. She betrays Catherine II's wishes, and Ellen meets with Edgar about all of this. But first, there is a portion worth noting here where Catherine II finally comes to terms with being the actual first cousin of Hareton. (Uhm, Hello, you want to marry your own cousin? There are a few issues here...)
Edgar proposes a vision to Ellen. He wish Catherine II marry someone that can console her when he passes. He sees the latter happening quite soon. He voices that he doesn't particularly mind that Linton is the son of Heathcliff, but rather he cares if the man he gives her up to is strong enough to provide and console his daughter.
This speaks volumes as to what point Edgar is at in his life. He sees that he had it all, without ever enjoying its entirety. He had a wife whom he adored, a daughter whom he adored as much, and so much more.
I have a feeling that this vision will come true to a certain degree. However, Mrs. Dean (Ellen) explains that these events happened within the past year. So we know for sure that Linton dies, for he is no longer at the Heights when Lockwood visits. Lockwood also voices to Ellen for the first time that he is considering courting Catherine II.
Lockwood is the first part of the end of Heathcliff's story, I gather. Lockwood is the realization of his vision of owning both the Heights and the Grange. It seems like an interesting twist or two as we snap back to currency are ahead...