Captain Cody - Sky Marshal of the Universe - saves the earth from the evil Moon Monarch.

A mysterious series of atomic explosions devastates America's industrial centers and military installations. A brilliant research scientist known as Commando Cody, Sky Marshal of the Universe, investigates, assisted by his co-workers Joan Gilbert and Ted Richards. Using futuristic, advanced scientific devices such as his jet powered flying suit and a rocketship capable of interplanetary travel, they attempt to track down those responsible for the attacks.

Determining that the explosions have been caused by a rare element called lunarium, found only on the Moon, Cody, Joan and Ted Fly there in the rocketship and discover a previously unknown lunar civilization. The Moon people are ruled by the evil Retik, who informs Cody that his people are dying because of the Moon's thin atmosphere,and that he intends to conquer Earth as a new home for his people. Retik tries to kill cody with a ray gun, but after a tense battle in Retiks laboratory, Cody escapes and returns to Earth with Joan and Ted. Retik, however, has sent his aide Krog to Earth so that they can emply criminals in their struggle against Cody. Cody, Joad and Ted must contend with Krogs henchmen, Graber and Daly, in a hectic series of rocketship chases and gun battles as they defend humanity from the Moon Men.

Frustrated because his plans have been continuously thwarted by Cody, Retik journeys to Earth himself in order to take personal command of the invasion. Krog and his thugs are finally defeated. Retik, attempting to escape back to the Moon in his rocketship, dies in a terrific explosion when Cody aims a ray gun at it.