"Ghost therapist" Dr. James Harvey and his daughter Kat arrive at drafty, old Whipstaff Manor. Its greedy owner, Carrigan Crittendon, has hired Dr. Harvey to exorcise the house's apparitions: a friendly but lonely young ghost named Casper, who's just looking for a friend, and his outrageous uncles Stretch, Stinkie and Fatso (The Ghostly Trio). If the plan works, she and Dibs, her partner-in-slime, can get their hands on the manor's fabled treasure. Casper finds a kindred spirit in Kat, but the Ghostly Trio will not tolerate "fleshies" in their house.