A would-be dictator and scientist, known only as The Phantom Ruler, has developed a formula which, when sprayed on some solid object, renders that object and everything it contains invisible when exposed to rays emitted by a special lamp, also his own invention. Covered from head to toe in formula-treated cloth, he thus moves about unseen, presently with the objective of stealing enough money and formula components to render an entire army of willing followers invisible. Two henchmen assist him, along with several illegal aliens smuggled into the US by him and used to infiltrate, as employees, possible sites for him to later rob while invisible. When he successfully robs a bank vault, an investigator from the bank's insurer teams up with a womanpolice detective to solve the mystery of the money which to all outside appearances has just vanished. Tracking clues and interrupting other attempts by the Phantom Ruler to commit crimes, the protagonists round up enough evidence that they are not merely dealing with an ordinary crime ring. Eventually they discover the invisibility fluid and lamp, and the Phantom Ruler is killed when he trips over an open high-power electric cable he had laid on the floor of his den to do in the forces of law and order closing in upon him.
Stanley Price as The Phantom Ruler. The villain of the serial uses the trappings of the Mystery Villain but his identity is revealed to the audience in the first chapter.
The Invisible Monster was budgeted at $153,070 although the final negative cost was $152,115. It was filmed between March 7 and 30, 1950 under the working titleThe Phantom Ruler. The serial's production number was 1707.
The Invisible Monster's official release date is May 10, 1950, although this is actually the date the sixth chapter was made available to film exchanges.
Television
The Invisible Monster was one of twenty-six Republic serials edited to a uniform runtime of 100 minutes and syndicated directly to television as a package of TV Movies in 1966. The title of this new version was Slaves of the Invisible Monster.
Critical reception
Cline describes this serial as just a "quickie." In Creature Feature, this movie serial was given three out of five stars, stating that the movie villain is incredibly inept and rarely uses his creation intelligently, and that the entire series is naive, but that there was an underlying sense of non stop fun.
Chapters
The Invisible Monster has 12 chapters. The first chapter is 20 minutes long, and each one thereafter is 13 minutes, 20 seconds. Chapter 10, "High Voltage Danger", is a recap of all previous episodes.
