The Fortieth Door

A mad scientist named Dr. Satan plots to steal key pieces of technology to enable him to build an army of robots based on his prototype to conquer America. The only one standing in his way is Bob Wayne, who fights Satan as the enigmatic Copperhead. Mysterious Doctor Satan is a 1940 film serial named after its chief villain. Doctor Satan's main opponent is the masked mystery man, "The Copperhead", whose secret identity is Bob Wayne, a man searching for justice and revenge on Satan for the death of his step-father. The serial charts the conflict between the two as Bob Wayne pursues Doctor Satan, while the latter completes his plans for world domination.

Richard Grant, imprisoned in India for a crime he did not commit, escapes and makes his way to Africa.

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.

Mystery and adventure, surrounding a stolen rubber harvest.

A Secret Service agent seeks his missing brother in Africa, and finds his mission complicated by ivory thieves, a girl with a mysterious past, and a troublesome gorilla.

Government agents try to thwart smugglers, while some sort of plot unfolds, about a hidden treasure revealed by cursed coins.

Wealthy Irving Randolph is falsely denounced as a deliberate murderer by his greedy younger brother when Randolph, during a rifle shooting contest, accidentally kills a man with whom he has had an altercation. Fleeing to Australia, Randolph becomes known as the bandit Stingaree and is aided in his Robin Hood like adventures by his friend Howie and his sweetheart Ethel.

The story of a boy, a dog, and a man. The boy discovers he is heir to a shipping line, and travels to Los Angeles, accompanied by inventor/radio operator Bob Whitlock and Irene Blaine. Their journey is aided by Pal, a wolf dog.

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.

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