We get power from many different sources, but we don't get it like the guys in Monstropolis do; they get it by capturing children's screams. By entering their bedroom's at night through their closet door teams of monsters power their city by scaring children!

Mike (Billy Crystal) is a little green monster with one giant eyeball and a short, round body. He, along with his teammate Sulley (John Goodman) a giant blue and purple fuzzy monster is just one of the teams that make their living by doing this.

There is one problem with the job they do; they're actually terrified of children! And when one girl named Boo follows Sulley back through the closet door to Monstropolis, the monster world is turned upside down!