In 19th century London, Dr. Charles Marlowe experiments with a mind-altering drug which causes him to develop an evil alter ego, Edward Blake, whom his colleague begins to suspect is someone that is blackmailing Marlowe.

• Amicus Productions
• British Lion Film Corporation
• Christopher Lee
• Peter Cushing
• Mike Raven
• Richard Hurndall
• George Merritt
• Kenneth J. Warren
• Susan Jameson
• Marjie Lawrence