Will Hunting (Matt Damon) comes from Southie, a rough district of Boston, and works at night as a janitor at the prestigious Massachusetts Institute of Technology (MIT). Will writes on some math class blackboards when no one’s looking, and Professor Lambeau (Stellan Skarsgard) discovers that Will is a natural mathematical genius. Lambeau tries to bring Will out of his go-nowhere environment into the academic world where his talent will be appreciated.

Will half-agrees, but he still hangs out with his tough crowd in Southie (including Ben Affleck as Chuckie), and he winds up getting arrested after a fight. Lambeau keeps Will out of jail through an arrangement that includes his mentoring plus Will’s going for psychotherapy with Sean McGuire (Robin Williams). That course of psychotherapy is the core of the film.

Sean’s treatment of Will in therapy involves lots of risks, but through a combination of empathy, rule-giving, self-revelation, and provocation, Sean manages to bring Will to understand that the severe physical abuse he suffered as a child at the hands of his foster parents is not his fault, and that he really is a good person who has a lot to offer. (This can sound corny unless you are the one who is making the discovery.)

Sean gains some credibility with Will when he admits that he, too, had suffered abuse as a child. Will’s realization makes possible a much more positive self-image and a whole new vision of life. He decides to stop denying his talents and to recognize that he might be good enough after all for brilliant and charming (and independently wealthy) MIT student Skylar (Minnie Driver), who loves him, and whom he finally leaves Southie to follow as she heads west for graduate school.