Sam Flynn doesn't want to run the soft-ware company founded by his father, Kevin Flynn (Jeff Bridges). He's given a beeper by his father's friend, Alan Bradley (Bruce Boxleitner, who portrayed TRON in the first movie) and this leads him to an old arcade. It's here that he crosses over to the virtual world his father created--and meets a whole slew of weird characters, including his father's doppelganger, Clu. Clu now rules this land and he's ruthless. Sam is forced to play in some games and is rescued by Quorra (Olivia Wilde) a woman who takes him to his father. He's glad to see his son but is not so receptive. Basically, the hero has to prevent the end of the world, as this digital world may invade ours and destroy it.
While by no means a great movie, this sequel is far far far better than the first TRON movie, which I was always bored to death with. The best improvement is that I don't feel as if I'm watching an antiquated video game.