The king can't sleep, so he asks his servants to read to him from Chronicles. That certainly put me to sleep. They happen to open the book to the section where Mordecai rats out the two conspirators against the king. That reminds Ahasuerus that he hasn't rewarded his gatekeeper.
He looks into the courtyard and happens to see Haman, who has woken up bright and early for the hanging. The king asks him how he should honour a man who pleases him. Haman, thinking he's about to get a reward, he asks for the kings used robes, horse, and crown. Think big, Haman. Then, to his utter shock, the king orders him to dress up Mordecai and parade him around on his horse. Haman has no choice but to obey. Then he goes home and sulks and bitches to his wife and friends. Then the king's servants arrive to remind him about Esther's second banquet.
The king and Haman arrive for the banquet. Before they even start eating, Ahasuerus is asking Esther to come out with her request, not that I blame him. She finally asks him to pardon the Israelites. Ahasuerus is so dumb he doesn't even remember granting permission to kill the Jews, nor who sought it. Esther points to Haman, who goes pale. The king goes out to the garden to cool off, while Haman makes the unwise decision to lay down on the same sofa as Esther. When Xerxes comes back, he thinks Haman is trying to rape her and orders him hoisted by his own petard.