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!

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!