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.

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.

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.

Prof. Millard pretends to be dead and helps Jeff King ferret out Vulcan, the evil traitor at the science academy. Donning his Rocket Man costume King goes from one hair raising rescue to the next in order to keep the newly invented Decimator out of the clutches of Vulcan and his minions.

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.

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.)

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.