Dave Karofsky tried to kill himself this week because the kids at his new school bullied him and spray painted "FAG" on his locker.
The action had an effect on everyone, as Sue was inspired to give Quinn her role back as a Cheerio and New Directions went on to win Regionals.
Kurt also gave Karofsky an encouraging vision of what his future could be like, ending the episode as his former bully's good friend.
How did the episode end? With Finn and Rachel about to get married... only for Quinn to get into a car accident on the way to get her bridesmaids dress.