The Great Radium Mystery

Man-woman team of investigators uncover a gang whose mad scientist leader has developed an invisibility chemical and plans to build a mercenary army of invisible men.

A Martian invader crashes his spaceship conveniently close to the workshop of a scientist who is developing an interplanetary craft. If the extraterrestrial Purple Monster can complete the rocket ship and return to Mars, he will be able to start a full-scale invasion of Earth. Good thing Craig Foster sets out to thwart the Monster's mission!

Claire Forrest seeks her kidnapped scientist father, hidden somewhere on Mystery Island. He is held and forced to work on diabolical inventions by Captain Mephisto, a costumed villain.

Dr. Ernst Grood , having already dominated the planet Ergro, now intends to take over the control of the Earth. Unfortunately for him, reporters oppose his sinister designs.

A famous scientist invents a humanoid robot (the titular "monster"), so a greedy rival scientist plans to steal it for use in his criminal plans. His henchmen often kidnap a trained gorilla (the titular "ape") from the zoo, to aid in the schemes.

An accomplished aviator sets out to locate treasure hidden by one of his ancestors. He encounters interference from various adversaries.

A newspaper publisher and his Korean servant fight crime as vigilantes who pose as a notorious masked gangster and his aide.

Two marine lieutenants battle a masked would-be world conqueror who uses electricity as a weapon.

Dick Tracy battles spies and saboteurs in his efforts to bring to justice the Stark gang, a criminal family led by the vicious Pa Stark.

Advertising man Roger Thornhill is mistaken for a spy, triggering a deadly cross-country chase.

Only Episode 7, "The Hooded Helper," of this 20-Episode Serial is known to survive. All other episodes are believed to be lost.

Captain Bob Dayton and Lieutenant Ed Carey are partners in a company called "Sky Raiders" which seeks US government contracts for its inventions. Enemy spies attempt to steal, sabotage and discredit the inventions and founders of the company.

Four youthful cadets are implicated in a series of murders, and must attempt to clear themselves of suspicion.

An escaped criminal impersonates a Police Commissioner, causing no end of trouble to a determined Federal Agent.

A 12-episode serial in which Tailspin Tommy evades volcanoes, anti-aircraft shells, and time bombs as he foils a plan by corrupt profiteers to steal an island's oil reserves.

Reporter Brenda Starr and her photographer Chuck Allen get involved in a search for the loot from a payroll robbery. Cliffhanging action and adventure and a fair amount of comic relief follow them at every turn.

Evil Hassan slips back into his native land of Ahad and plots to overthrow his twin bother, Kasim, who has just been crowned the Caliph. Hassan enlists the aid of the chief Chamberlain, Faud and they send several henchmen into the royal palace, who then knock Kasim unconscious. Faud and Hassan dispatch a couple of different hirelings to take Kasim into another part of the town and murder him.Kasin comes to and gets away, but has been wounded. Omar, a beggar, takes Kasim to his home and nurses him back to health. But, it takes a few weeks for Kasin to get healthy and, by that time, Hassan has a firm grip on the duties of a Caliph. In a storeroom, Kasim finds a coat of mail with a great hawk emblazoned across the chest and promptly decides this is the costume he will wear while fighting to get his old job back. Meanwhile, the Emir of Telif shows up with his daughter, Princess Azala, with the intent of marrying her off to the local Caliph.

Daniel Robin has become mixed up with a band of criminals known as "the 13," and is shot when he refuses to do their bidding. His daughter Ruth, brought home from boarding school, reaches his bedside before he expires. He tells her that she will be given thirteen keys. Instructions will be provided with each key and, if she follows the instructions, she will eventually fully learn of her birthright. Many adventures then follow as Ruth attempts to solve the puzzle of each key and establish her true birthright.

The mysterious Don Del Oro ("Lord of Gold"), an idol of the Yaqui Indians, plans to take over the gold and become Emperor. Francisco was put in charge of a legion to combat the Yaqui tribe and protect the land, but when attacked Zorro came to his rescue. Francisco's partner recognized Zorro as the hidalgo Don Diego Vega, then ask him to take over the fighting legion as his alter-ego Zorro.

Special Agent Kanen must follow the target of his latest case -- but what happens when the target has connections to his mysterious past?