A monster called Que Horrifico is turning the children of Crystal Cove into monsters, prompting the parents to move away. At school, Fred is being tutored by Mary-Ann Gleardon, who believes she’s too smart for everyone. To help solve the mystery, Velma and the gang speak with a teacher at school who is familiar with Que Horrifico but believes he turns into the monster at night. They agree to watch him for the night, only for the real Que Horrifico to appear, commanding the children attack the gang. The gang accidentally turn a television on, and the children sit down to watch, revealing themselves to simply be pretending to be monsters. The gang traps Que Horrifico, who is revealed to be Mary-Ann, who wanted a Crystal Cove with no adults so she could turn the city into her utopia.
