While driving back from the movies, the gang finds a strange man in the back of the Mystery Machine. They recognize it as the ghost of Mr. Hyde who is a jewel thief. They follow him to a house where they meet a descendent of Dr. Jekyll who claims to be the ghost of Hyde, but is he telling the truth?
Quest roles:
Casey Kasem(Shaggy Rogers (voice)), Don Messick(Scooby-Doo (voice)), John Stephenson