The Hazards of Helen

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

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.

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

An expedition arrives on an uncharted jungle island to rescue the local natives, led by a jungle boy, from a volcano that is about to erupt.

Escaped Prisoner 39013 impersonates the rich and influential Horace Granville, allowing him to create a variety of disasters. Fortunately, he is thwarted repeatedly by three daring circus daredevils.

Two British officers are assigned to collect information to convict Captain Kidd of piracy.

Mota is a Martian representative, who has come to impose interplanetary law on the Earth (which has become too dangerous); opposing his authority is Kent Fowler, who resists the alien plot, without understanding its details.

Prior to the United States' involvement in World War II, the masked vigilante Spy Smasher fights Nazi agents operating within the US, led by the treacherous sabotage leader codenamed The Mask.

A young girl journeys to Africa to find her father, an explorer who vanished in the jungle.

Beyond Hell's Gate Pass is territory controlled by a man who calls himself King Carter; he uses a variety of schemes to prevent the railroad from being built, for fear it will finish his control of (what he considers) his land.

The obsessive scientist Dr. Miller is working on a matter-transmitter invention called the Paratron; a conspiratorial team of spies and no-goods pursue him to Alaska, trying to steal the device.

Jerry Blake (aka Federal Operator 99) teams-up with Joyce Kingston to thwart the plans of escaped crime boss Jim Belmont.

Tom King Jr. seeks to discover who murdered his father, a Texas Ranger; the trail leads to a network of Axis spies.

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.

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.

Calvin Drake employs a group of low-lifes to drive away land owners along the path of a new railroad; Red Ryder opposes this strategy.

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.

A police detective is caught up in a plot to steal two million dollars in bonds.

An Indian rug is the key to the location of a lost treasure. When the rug's owner is murdered, it becomes a case for Forest Ranger Steve King

The nefarious Dr. Fu Manchu searches for the keys to the tomb of Genghis Khan, in order to fulfill a prophecy that will enable him to conquer the world. His nemesi, Dr. Nayland Smith and his associates fight to keep the evil doctor from getting his hands on the keys. In 1943 the serial was edited together into a feature movie also called Drums of Fu Manchu.