Children are so afraid of monsters at night and use it as an excuse as to why they can't sleep. Have you ever wondered if those monsters were more afraid of humans than we are of them? In this animated movie this is just the case. Monsters go through extensive training to know exactly how to scare the children they are assigned. The idea is to be so scary that the child does not want to come near the monster since all monsters think that humans are very toxic. It is rumored that one touch will kill a monster. As a precaution, all monsters are immediately shaved, showered and quarantined if they touch anything that has ever been touched by a child.
Monsters named Sully and Mike both live together and work at Monsters Incorporated. At this company, monsters place child specific doors on a machine and then walk into the real world to scare the assigned children. The screaming that is produced by the children is captured in bottles, which is what powers the monster's world. Sully is the best scarer in the company. Once a child grows up and is too old to be scared of monsters, then the door is ground into wood chips.
Randall is another monster at Monsters Inc. He is very competitive and is always trying to get more screams bottled than Sully. He is a lizard that can look exactly like his surroundings which makes him look invisible.
Mike's girlfriend's birthday is today. Mike is in charge of documenting the volume of screams each day produced by Sully. Today, Sully decides to cover for Mike so he can take his girlfriend out to dinner. The only thing is that Mike hasn't done the paperwork in a few days so he is in the office for a while. Sully notices a door that is still on the machine. Sully checks the door to make sure that no monsters are in there. Once he closes the door he feels something on his tail. The child is now in the Monster's world standing right behind him. At first he is very scared since one touch from a child can kill him, but he tries to return her to her door. Randal comes out of her door instead. Sully does not want the child to be discovered in the monster's world so he hides her. Randall returns the door and key and calls it a night.
Since her door is gone now, Sully puts the child in a bag and takes her to Mike at the restaurant for advice. The child gets loose. Mike, Sully and the child escape before the area is sterilized. Sadly, Mike's girlfriend was not so lucky and later gets very mad at him for leaving her at the restaurant.
They take the child back to their apartment. She thinks everything is funny until Mike takes his teddy bear away from her. This makes her cry and all the lights start overcharging. They quickly try to give her the bear but trip and fall. This makes the child laugh which blows all the lights in the area. They decide to put her back the next day by disguising her as a baby monster and claiming that she is his cousin.
They decide to name the child Boo. Boo is very good at disappearing. Sully even thinks that she is thrown in the trash by accident once when she disappeared and is ground in to tiny pieces. She finds her way to the childcare part of the company and is found later by Sully. Randall approaches Mike and tells him to bring the child to the door when everyone is at lunch. They do, but Mike tests out the room first in case it is a trap. Randall captures him and takes him to the machine in the basement. This machine would give him the lead over Sully if he had the child. Sully and Boo follow and save him. Once Mike and Sully escape, they bring the child to Mr. Waternuce, the president of Monsters Inc. and find out that is really behind Randall's kidnapping actions. He throws the monsters through a door to the Himalayas. There they become friends with the abominable snowman where they have their fill on snow cones. How will they get back to save Boo? Will Boo ever be returned to her door? Watch and find out.
