Scooby-Doo and the Witch's Ghost (1999)

When the Mystery Gang meet famous horror writer Ben Ravencroft (Tim Curry) on their last mystery, he invites them to the small town Oakhaven, Massachusetts. While there for the Autumn Harvest Festival, Ben explains the history of his ancestor Sarah Ravencroft, who happens to be an evil witch. At the same time, the Hex Girls, an all-female Gothic rock band, come to town bringing an audience there. The gang investigate the mysterious sightings while they are there which seems to be connected to the locals of the town which turns into something much more.