Ranbo, a math professor at MIT, announced a math problem at the meeting, but it was solved by the young cleaner Will (Matt Damon). However, will is a problem for teenagers. He hangs out with his good friend Chuck (Ben Flatt) and others all day, fighting and making trouble. When Ranbo discovered this genius, he was sent to the detention center for fighting and assaulting a police officer. Ranbo asked the judge for bail, which saved him from jail.

In order to let Will find his goal in life and not waste his talent in mathematics, Ranbo invited many psychologists to tutor Will, but Will resisted, and the experts were helpless. At the end of his rope, Ranbo turns to his college friend and professor of psychology, Shane (robin williams), hoping to help Will open his heart.

Through the unremitting efforts of Ranbo and Shane, Will gradually opened his mind, and his good friend Chuck's words made him suddenly enlightened.