James Sullivan and Mike Wazowski are monsters, they earn their living scaring children and are the best in the business... even though they're more afraid of the children than they are of them. When a child accidentally enters their world, James and Mike suddenly find that kids are not to be afraid of and they uncover a conspiracy that could threaten all children across the world.
In order to power the city, monsters have to scare children so that they scream. However, the children are toxic to the monsters, and after a child gets through, two monsters realize things may not be what they think.