When the spaceship Saturn embarks from Long Island Spaceport, radio operator Sparks Donovan is startled by a secretive visit from the ship's captain, Cap Hanson. Hanson reveals that their First Officer, the quirky yet brilliant Lancelot Biggs, is being secretly examined by an undercover inspector from the Space Safety Control Board, posing as a quarantine officer. The test aims to see if Biggs is fit to command his own ship.

Sparks must subtly warn Biggs to avoid any experimental antics during the voyage, but chaos ensues when Biggs unwittingly causes a ship-wide malfunction. With the inspector enraged and Biggs' promotion in jeopardy, can Sparks to unravel the mayhem and help his friend prove his worth?