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 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.
Greedy traders have kidnapped a researcher, hoping he will reveal the location of a treasure in a hidden village. Family and friends of the researcher come looking for him. Adventure ensues.
A team of two-fisted insurance investigators (one of whom disguises himself as The Masked Marvel) endeavor to discover and thwart the loathsome saboteur Sakima.
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 newspaper publisher and his Korean servant fight crime as vigilantes who pose as a notorious masked gangster and his aide.