1) Mordecai refused to bow down to Haman, angering him and causing Haman to plot to kill all Jews in the kingdom.
2) Esther and the Jews fasted and prayed for three days to ask God for help.
3) The king couldn't sleep and learned of Mordecai's past good deed, leading to Haman being hanged and the Jews being saved.
4) Jews celebrate the Feast of Purim each year to remember being saved through fasting and prayer.