Casper is a kind young ghost who peacefully haunts a mansion in Maine. When specialist James Harvey arrives to communicate with Casper and his fellow spirits, he brings along his teenage daughter, Kat. Casper quickly falls in love with Kat, but their budding relationship is complicated not only by his transparent state, but also by his troublemaking apparition uncles and their mischievous antics.

When a warlock threatens Wendy the Good Little Witch, she and her aunts hide out at a resort where Casper the Ghost is vacationing with his uncles. Although Casper and Wendy are told ghosts and witches don't get along, the two are kindred spirits! This spooky family-friendly adventure finds Casper and Wendy bridging the ghost-witch divide to battle the warlock who is intent on destroying Wendy.

Before he met and befriended the other ghouls at Applegate Manor, friendly ghost Casper meets young Chris Carson, a lonely kid who decides to teach Casper how to be a proper ghost.