Monsters, Inc. is a story about Monstropolis, a city where monsters are forced to generate energy from the screams of children. The entire society is scared of being contaminated by kids. The two main characters, Mike and Sulley, allow a child to enter their world, and they hide the child that they name "Boo" because they don't want to be decontaminated. Boo turns out to be a lot of trouble. Mike and Sulley end up having to shield Boo from all of the other monsters. While they are skeptical at first, Mike and Sulley become attached to Boo, and at the end of the movie when they are forced to bring her back to her house, they are upset.