After living peacefully in the caverns of a small town, a stranded group of aliens turn deadly as they fight for their existence, betraying the passionate chief of police who has protected them for 28 years.
Scooby-Doo and Shaggy must go into the underworld ruled by the Goblin King in order to stop a mortal named The Amazing Krudsky who wants power and is a threat to their pals, Fred, Velma and Daphne.