While staying at Whipstaff Manor in Friendship, Maine, the Mystery Incorporated Gang meets paranormal therapist Dr. James Harvey, his teenage daughter Kat, their ghost friend Casper, and Casper’s three mischievous uncles Stretch, Stinkie, and Fatso (better known together as the Ghostly Trio), who need help with getting to the bottom of a series of mysterious hauntings in town that, for once, are not the Ghostly Trio’s doing.
