Who is The Phantom Ruler? That's the question posed by the 12-part Republic serial The Invisible Monster. Using four illegal European aliens as his minions, the Phantom Ruler-possessed with the power of invisibility, as indicated by the title-goes on an unchecked crime spree. Insurance company investigator Richard Webb (later TV's Captain Midnight) is assigned to determine the identity of the Phantom Ruler, and to put the cuffs on him. Both Webb and his assistant Aline Towne are subjected to any number of life-threatening perils before justice is meted out in the final chapter. One of the best of the later Republic chapter plays, The Invisible Monster is also available in a 100-minute feature version, The Invisible Monster Strikes.