Kibosh, the supreme ruler of the ghosts, gives Casper an order: Scare at least one person by Christmas Day. Casper's mission takes him to Kriss, Massachusetts, where he meets his intended victims, the Jollimore family. Casper has a hard time giving the Jollimores a real scare -- so his wicked uncles, the Ghostly Trio, recruit Casper's cousin Spooky to fulfill the mission.