At the start of the episode, the Super Friends are involved in an intense outer space battle. Moments into the battle, Wonder Woman gets a telepathic message from Aphrodite to help save the planet from a disturbance. Afterwards, all of the Super Friends show up and Aphrodite praises them on their great work and good will. An envious Hera gets into an argument with Aphrodite on Mount Olympus, which triggers the wrath of Zeus. Hera criticizes Aphrodite for praising "mortals" such as the Super Friends and she suggests to Zeus that the Super Friends are not as powerful as Aphrodite claims. Zeus then creates a contest in which each of the Super Friends must do battle with mythological demons in an effort to prove they are worthy of Aphrodite's praise. Batman and Robin must battle a Sphinx and solve its riddle, Aquaman has to fight a demon that protects the Golden Fleece, Superman battles a Minotaur, and Wonder Woman has to battle Medusa. The Wonder Twins get mixed up in all of this when they see Medusa in the shadows and mistake her for Wonder Woman...and once they look into her eyes, they turn to stone. Gleek manages to escape Medusa's clutches and ends up aiding Wonder Woman in removing Medusa's necklace. By the episode's end, the Super Friends prove to be worthy of Zeus's praise.

Aquaman is exposed to a radioactive substance that turns him into a prehistoric sea creature from which he evolved. In order to cure him, Superman and Wonder Woman, inside the Supermobile, are shrunk down to microscopic size and sent within the creature's veins to attempt to give it another dose of radiation in the hopes that it will reverse the effects of the radiation and return Aquaman to normal. In the meantime the rest of the Super Friends have to do whatever they can to limit the creature's destructive nature all over the city.