When the ancient continent of Mu sank beneath the ocean, some of its inhabitant survived in caverns beneath the sea. Cowboy singer Gene Autry stumbles upon the civilization, now buried beneath his own Radio Ranch. The Muranians have developed technology and weaponry such as television and ray guns. Their rich supply of radium draws unscrupulous speculators from the surface. The peaceful civilization of the Muranians is corrupted by the greed from above, and it becomes Autry's task to prevent all-out war, ideally without disrupting his regular radio show.

Flash Gordon, Dale Arden and Dr. Zarkov return to the planet Mongo for an antidote to the Purple Death, which wreaking destruction on Earth. However, Ming the Merciless has other plans for them.

Strategic targets on Earth are being destroyed by an unknown weapon. Government security head Henderson suspects it's an "atomic ray" originating from the moon! He assigns Commando Cody, scientist and man of action with a secret flying suit, to investigate. Soon, Cody is battling Earth thugs in the pay of Krog the moon man and making trips in his experimental rocket to the moon itself, in a perilous and all but singlehanded effort to thwart the planned invasion of Earth.

From his secret laboratory, Captain Z-Ro and his associates use their time machine, the ZX-99, to learn from the past and plan for the future.

Superhero Captain America battles the evil forces of the archvillain called The Scarab, who poisons his enemies and steals a secret device capable of destroying buildings by sound vibrations.

Crash Corrigan, a recent graduate of Annapolis, and Diana, a go-getting reporter, join Professor Norton for a search for the source of a string of earthquakes, Atlantis. They ride Prof. Norton's rocket submarine searching the sea and little Billy Norton, the professor's son stows away, of course. When they find Atlantis they are caught in a war between peaceful Atlanteans, note their white capes, and war-monging Atlanteans, note their black capes. After many harrowing moments for Crash, Diana, Prof. Norton and Billy, they barely get away with their lives when they escape a tower of Atlantis raised to the surface for the sole purpose of dominating or destroying the Earth (Which one depends on the compliance of the upper world dwellers.)

Animal trainer Clyde Beatty heads a rescue party in search of his girl, Ruth, and her father who get lost looking for an uncharted island. His dirigible crashes into the jungles of the island. When he locates Ruth, he learns that her father has disappeared. The ensuing search is hindered by greedy gold hunters and wild animals.

A military intelligence officer and a pretty reporter try to find a scientist whose inventions can destroy the world.

A young couple journeys to Mystery Island to rescue the girl's father, who is being held prisoner by the evil Captain Mephisto, a pirate from 200 years ago who uses his Transformation Machine to travel forward in time and disguise himself as one of the four owners of Mystery Island.