Captain Video discovers a race of mutant plantlike humanoids on Jupiter's moon Iona.
Ranger Craig, a rookie with the Video Rangers, discovers and helps defeat a plan by Prince Spartak and his colleague Princess Arura who have both contrived a deceitful plan to invade the Earth's moon by using the pretext of visiting on a peaceful mission.
The Video Ranger's behavior has changed and is a matter of concern to Captain Video, who moves to investigate.
It's a duel of wits between Captain Video and John, whose brain has a computer assist.
Captain Video is in a secret and extremely remote location.
A starship on its way to Earth is struck by a meteor, and all communications and guidance systems are lost.
Captain Video's allies on the giant starship are endangered by the threat of collision with Earth's orbit, and he strives to save the ship.
With the Galaxy wrecked, Captain Video's resources are limited as dangers mount.
A desperate race ensues for the Philosopher's Stone between Captain Video and the criminal Zazarion, both sides seeking to unlock the secrets of matter and energy within.
The race for the Philosopher's Stone intensifies as Zazarion struggles with Captain Video. Prince Spartak arrives in support of the Captain.
As the Captain and Ranger return to Earth, it begins to appear that McRorrity may have plans of his own towards an adventure that isn't yet obvious.
Out of control, the Captain's ship GALAXY crash-lands.
Both McRorrity and Radig have had their minds altered by a device.
A crisis develops when the Captain and the Ranger are only able to use one space helmet.
The GALAXY is gravely imperiled.