The first entry in the "Morlock" series. Cub reporter Janet Lawton of The Dispatch(played by superstar Mara Marini) behgs her boss Ed Thicke (Edward G. Robinson) for a chance at making her name as an investigative muckraker. Grudgingly, he sends herto check out strange doings at the abandoned insane asylum on the edge of the city. She discovers that once-brilliant research scientist Leopold Morlock (played by fourth-billed Jesse Merlin, a star with the Barstow Opera Company appearing in only his third film) is in residence and conducting experiments on a silent young woman known only as "Ghoul Girl" (played by starlet Amy Ball in her film debut) with the hopes of tranplanting her brain in to a gorilla so that he canm rule the world. Morlock immediately realizes that Janet is a better match so he shrinks his evil assistant Ruprecht (played by "B" movie character actor Tom Ackerman) to miniature size so that he can kidnap an ape from the research lab at the university who discredited Morlock and had him sent to the asylum. The mad doctor manages to capture Janet and tie her up in her underwear and prepares to perform the operation but just before the switch is flipped, Janet's love interest, no-nonsense cop Jack Mannix (played by heart throb Jonny M.), breaks into the lab and shoots Morlock dead.
The studio had low expectations for the film and rushed it out to capitalize on the popularity of top-billed Mara Marini after her star-making debut in the film noir hit "Dame with a Gun." Executives were stunned when it became their number one box office hit of the year and that Merlin received as much fan mail as Marini did. Plans were immediately made to create a sequel.