Casper, a ghost, teams up with Wendy, a witch, against an evil warlock.

Living under the care of his uncles, the Ghostly Trio, Casper has been letting them push him around and making his afterlife miserable by having him do chores for them while they are scaring "fleshes" for their amusement. While taking a vacation, he meets with a good little witch named Wendy, as she and her bewitching aunts are on the run from an evil warlock named Desmond Spellman who attempts on destroying her after discovering that she will be a greater witch than him. Like Casper, she is a kind witch who also has her relatives mistreating her. They become good friends as they discover that ghosts and witches are each other's worst enemies, so they come up with a plan to make their relatives pair up to one another. Once Desmond comes to town, he determines to destroy Wendy at once. It is now up to Casper as he must get the courage to convince his uncles to help him to save Wendy and her aunts from Desmond.

Casper is back, and now he is on vacation with his uncles, the Ghostly Trio. While on vacation, Casper runs into the good little witch named Wendy, as she and her aunts are on the run from an evil warlock named Desmond Spellman who plans to destroy her after figuring out that she would surpass him by being the greatest witch of all time. Now she and Casper must work together to stop Desmond from fulfilling his plan, even if it means trying to get their respected relatives, who are natural-born enemies to get along.