The Invisible Dr. Mabuse: A beautiful dancer is terrorized by an invisible man, and FBI agent Joe Como (Lex Barker again!) is out to catch the killer of a fellow agent. At the heart of the mystery is "Operation X," an invention capable of giving unlimited power to its owner. Is Dr. Mabuse behind the danger, or is the invisible being something even more sinister? Find out in this thrilling mixture of mystery, intrigue and a dash of Phantom of the Opera.