As a result of Casper being too friendly with a boy named Jimmy Bradley and failing to scare enough humans Kibosh: The King of the Underworld has Casper enrolled into a Scare School, to prevent him from being banished into the Valley of the Shadows, headed by the two-headed headmaster Alder and Dash. At Scare School he befriends Ra, a mummy with unraveling issues and Mantha, a zombie girl who keeps falling apart.