Casper, a friendly ghost who lived in an abandoned mansion called Whipstaff Manor in Friendship, Maine, along with his three obnoxious, ghostly uncles, Stretch, Fatso, and Stinkie, has been hoping to find a friend for over one hundred years. When a spoiled woman named Carrigan Crittenden is angry about her late father's will to Whipstaff, she soon discovers that there is treasure hidden inside it, so she along with her partner, Dibs, arrive to seek it out. When Casper introduces himself to them, they are frightened by him and his uncles who scares them off, leading them to try several attempts to get them out of there, but to no avail. Thanks to Casper, they hire Dr. James Harvey, a ghost therapist who contacts with the living dead and helps them crossover to the other dimension while trying to search for his deceased wife. Once he arrives along with his daughter, Kat, Casper develops a crush on her and tries to make friends with her and James, but his uncles attempt to scare them away.