Esther is preparing the second feast for King Xerxes and Haman - this is when she is going to ask the King to save her people. 

But, the night before the feast, the King couldn't sleep. He asked for his book of records to be brought to him. As he was reading, he was reminded that Mordecai helped stop a plot against him, and asked what had been done to reward Mordecai. Nothing - he had not been rewarded. 

King Xerxes sends for Haman and asked him what should be done to reward someone who helps the King. Haman thought the reward was for him, and when Haman answered, the King told him to do that for Mordecai! 

So, to reward Mordecai, Haman had to walk around the city pulling a horse with Mordecai while yelling that Mordecai did a great thing for the King. How humiliating!

Later, it was time for the feast. Esther bravely said to the King: save me and my people, for they are going to be killed. 

The King was upset. Who was trying to kill her people? He didn't know what Esther was a Jew. But, it was Haman, so Haman was punished.

While God isn't specifically mentioned in the story, we can see how God was working this story for the good of His people. 

Let's compare King Xerxes to God our King: