The Mystery Machine arrives at the ruined castle, and the gang climb out, ready to explore. Suddenly, Velma, Shaggy, Daphne and Fred are seized by large hands and a chorus of voices cry out, "Our experiments are almost complete. Nothing can stop us now!" Though frightened, Scooby decides to looks for his friends, but soon has the feeling that he is not alone. Ghosts and demons of the strangest kind gather on all sides and appear out of doorways, intent on stopping him freeeing the rest of the gang. Can you, as Scooby Doo, fight your way through the mad scientists' henchmen to rescue your friends, then seek out their captors? Perhaps the trail of Scooby Snax may help you in your search.