James P Sullivan has a very important job. He scares kids because their screams provide power to the city of Monstropolis. He's the top Scarer at Monsters, Inc. It's nothing personal, it's just his job. But being a Scarer is dangerous, because as every monster knows, human kids are toxic.
Now Sulley has made a huge mistake - he has let a human child into the monster world! Can Sulley return the little girl to her home before Monstropolis is destroyed?