For a three-act plot analysis, put on your screenwriter’s hat. Moviemakers know the formula well: at the end of Act One, the main character is drawn in completely to a conflict. During Act Two, she is farthest away from her goals. At the end of Act Three, the story is resolved.
Act I
Timon throws wild parties and gives out way too many pricey gifts, only to realize that he is in huge debt to just about everybody. He tries to fix his spending habit by borrowing from his friends, but nobody wants to lend anything to him.
Act II
With nothing to do and nowhere to go, Timon heads off to the woods in exile. He just wants to be alone and forget that he—or anyone else—ever existed. He's not totally successful: he camps just outside of Athens, where people come to visit him in his cave. He wants disease and misery to be brought on everyone in Athens, so he helps Alcibiades with his bid to take over the city.
Act III
Timon mysteriously dies in the woods and leaves a grim and cynical epitaph for the world to see. The upside? Alcibiades takes over Athens and promises to restore order and peace, with a side order of justice.