But we get a few more details, courtesy of the Nick grapevine:
Daisy was the first "nice" girl Gatsby had ever known or met. His initial plan was to get some backseat action, but then he accidentally fell in love. (It happens.)
There's a great discussion of class and wealth here. Gatsby felt uncomfortable in Daisy's house – she was simply from a finer world than he. When he finally "took" her (in the sexual sense of the word), it was because he wasn't dignified enough to have any other relationship.
Nick reveals that Gatsby misled her, too, making her believe he was in a position to offer her the safety and financial security of a good marriage, when in fact all he had to give was some lousy undying love.
In the war, Gatsby did well for himself (medals and such). He tried to get home as soon as the war was over, but through some administrative error or possibly the hand of God, he was sent to Oxford.
Meanwhile, Daisy got tired of waiting for him and married Tom (right after the drunken sobfest we heard about earlier).
Gatsby, desperate, tries to figure out what will happen "now." He tries to reassure himself that Daisy does still love him and that the two of them can live happily ever after.
In an ominous moment, one of Gatsby's servants details that he's going to have the pool drained. Gatsby comments that he hasn't used the pool all summer.
We suspect that's going to become important in about half a chapter.
As he leaves, Nick reveals his feelings for Gatsby when he says, "They're a rotten crowd […]. You're worth the whole damn bunch put together." And YET, Nick reminds us that he "disapproved" of Gatsby "from beginning to end."
Once he's at work, Jordan calls him on the phone. They are both sort of cold to each other. Their status just changed from "in a relationship" to "it's complicated."
No, wait, they are both now officially "single." Nick is just sick of the entire crowd and doesn't want to have anything more to do with them.
Back to the Myrtle death story. We find all of this out from Nick who found out from Michaelis (or possibly some other intermediary):
Wilson, in the midst of his grieving, revealed that he had recently started to suspect his wife of having an affair. He had found an expensive dog collar in her room (from Tom) and huge bruises on her face one day (also from Tom).
Wilson came to the sudden conclusion that whoever was driving the car was the same man having an affair with his wife.
Before she died, Wilson had taken his wife over to the window and told her that she couldn't fool God – that God was always watching. Conveniently, the large eyes of T.J. Eckleburg emerged visible from the fog.
And that's the end of that menacing little story.
Back in present time, Wilson goes on a crazy vengeance mission to find out who owns that yellow car. He, of course, ends up at Gatsby's house.
Gatsby, meanwhile, has decided that it's time to use that pool of his.
Shots are fired.
Nick ends up at Gatsby's house, and together with the staff discovers that Wilson has shot Gatsby and then himself. Both are dead.