On their way home from the Malt Shop, the gang encounters the Ghost of Mr. Hyde in the back of the Mystery Machine, who runs through a marsh and sneaks into a spooky house. The house turns out to be the home of Dr. Jekyll (the great-grandson of the novel character), who fears he may be transforming into the ghost. The gang begin searching the house for clues, pegging Helga, Jekyll’s housekeeper, as a likely suspect, but they are pursued at every turn by the ghost.
