“I’m still your ruler, and I’ll not stand for any half-hearted obedience.”

An evil scientist who calls himself The Phantom Ruler (Stanley Price) hatches a plot to take over the world. His plan is to create any Army of invisible soldiers. He has created a formula that, when applied to anything, and subject to the light from a special lamp, will render that object invisible. The Phantom Ruler sprays the formula onto cloth and covers himself from head to toe. It looks kinda like a ninja outfit. Covered in the treated cloth, and with his special light, he can render himself invisible and go about doing evil deeds.

Creating an Army of invisible soldiers takes money. Lots of money. To finance his operation The Phantom has his henchmen smuggle into the county several illegal aliens. He positions these people in jobs with companies that The Phantom believes may be beneficial to him. To get the money he needs he uses the illegals to help him get into these companies where he can either rob them or use their secrets to his advantage.

One of his crimes is to rob a bank vault. The bank calls in an insurance investigator, Lane Carson (Richard Webb), to investigate the robbery. Assigned as his aide is a female detective, Carol Richards (Aline Towne).

With not much to go on, Lane and Carol doggedly track the thieves and foil each new attempt by The Phantom to gain enough money to fulfill his destiny. Each crime brings them closer to the head of this nefarious crime ring.

“The Invisible Monster” was released in 1950 and was directed by Fred C. Brannon. It is a short Republic film serial. The Invisible Monster was one of twenty-six Republic serials re-released as a film on television in 1966. The title of the film was changed to “Slaves of the Invisible Monster”. This version was cut down to 100-minutes in length.

It plays sort of like a hard boiled detective story. Lane is the handsome lantern jawed insurance investigator. Carol the tenacious sidekick. She can match Lane in everything he does, all while wearing heels and carrying a purse.

It’s a short but busy little serial. Lane and or Carol manage to get themselves into two predicaments per episode, one in the middle and one as the cliff hanger, as well as at least one fist fight and a couple gun fights per episode. Dynamite is in no short supply nor are the number of rounds in each gun.

My only “what the?” about the movie is this; in order for the Phantom to be invisible he needs to wear a ninja outfit treated with his nifty little invisibility formula. While he is wearing his ninja outfit he also needs to have a special light shine on him. Fine. You can’t see the ninja but what about the huge canvas truck with the giant spotlight and the guy working the spotlight. Even if no one notices a spotlight on wheels, how is The Phantom going to pull off an army of such ninja clad minions toting their own spotlights? I would hope they are at least battery operated. After all, extension cords can be such a nuisance.

Chapter Titles: 1. Slaves of the Phantom; 2. The Acid Clue; 3. The Death Car; 4. Highway Holocaust; 5. Bridge to Eternity; 6. Ordeal by Fire; 7. Murder Train; 8. Window of Peril; 9. Trail to Destruction; 10. High-Voltage Danger; 11. Death's Highway; 12. The Phantom Meets Justice. 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.