The Ultimate Vampire Resource and Directory

Featuring the evil science experiments of Dr Jekyll ...

Slim (Bud Abbott) and Tubby (Lou Costello) are American cops in London studying police tactics. A newspaper reporter, Bruce Adams (Craig Stevens), gets into an altercation at Hyde Park that was instigated by Vicky Edwards (Helen Westcott), a suffragette. Bruce and Vicky wind up in jail, while Slim and Tubby are kicked off the police force. Dr. Henry Jekyll, Vicky's guardian, bails them out.

Jekyll has been conducting home experiments in which he injects a potion and transforms into Mr. Hyde, a monster who murders a fellow doctor when he scoffed at Jekyll's experiments. Jekyll has more thoughts of murder when he notices that Vicky and Bruce are mutually attracted. Tubby and Slim witness the doctor's shenanigans at a music hall, where they begin to chase him with Bruce at their side. Tubby traps Hyde in a wax museum, but by the time he brings the Inspector (Reginald Denny) and Slim to the scene, the monster has already reverted back to Dr. Jekyll. The "good' doctor then asks Slim and Tubby to escort him to his home, where Tubby drinks a potion that transforms him into a large mouse. Slim and Tubby bring news of Jekyll's activities to the Inspector, who refuses to believe them.