Monstropolis, present day. At Monsters Inc., Sulley (voiced by John Goodman) and sidekick Mike (voiced by Billy Crystal) are the top scaring team on the job. Their task is to keep Monstropolis ticking over, running it on the power generated by children screaming - a production line of assorted terrifying monsters are sent to appear in front of children by passing into Earth through special dimensional portals then bottling the screams thus produced. Believing children are toxic, dangerous creatures who must be kept out of Monstropolis at all costs, Mike and Sully are terrified when they realise that a little girl called 'Boo' has followed them back through a door. Slowly they realise that little Boo isn't actually dangerous at all and uncover a sinister plot that exists behind Monsters Inc's happy facade, involving creepy arch-rival scarer Randall (voiced by Steve Buscemi).