When 12-year-old Trevor McKinney begins 7th grade in Las Vegas, Nevada, his social studies teacher Eugene Simonet gives the class an assignment to devise and put into action a plan that will change the world for the better. Trevor's plan is a charitable program based on the networking of good deeds. He calls his plan "pay it forward", which means the recipient of a favor does a favor for three others rather than paying the favor back. However, it needs to be a major favor that the recipient cannot complete themselves. Trevor does a favor for three people, asking each of them to "pay the favor forward" by doing favors for three other people, and so on, along a branching tree of good deeds. His first good deed is to let a homeless man named Jerry