A Space Academy tournament, consisting of sports, a written exam, and a space race, pits the Polaris unit in competition against other Cadet units at the Academy. The chief competition is the Vulcan unit led by Eric Rattison. Controversy cast a shadow over the Polaris unit when evidence indicates that a member of the Polaris crew has stolen an examination paper from Dr. Dale's office.

An apparent plan by the Solar Council on Mars to break up Space Academy into three separate Academy's actually masks a much more sinister plot to start a revolution with the goal of destroying the entire Solar Guard.The Space Cadets wind up imprisoned inside an old rocket that has been programmed to go out of control and crash into the Martian surface.

Astro is believed to have contracted "Space Fever" a disease which could result in having him permanently grounded from space travel, and thus, out of the Polaris Unit. During his narration, Frankie Thomas defines for the viewers just what a 3-man Space Cadet unit, like the Polaris, really is.

The Space Cadets, along with Captain Strong, Commander Arkwright, and Dr. Joan Dale, seek an Academy scientist lost on a distant planet in an uncharted solar system. Their search takes them to the legendary Rocket Graveyard, where dozens of lost ships have accumulated over the past 200 years. The graveyard appears to be otherwise deserted, but there are unknown foes waiting -- not all of which are human.

A clue provided by a youthful stowaway provides the only hope of preventing Roger and Captain Strong from making contact with an anti-matter asteroid and instantaneous annihilation.