The Lightning League are once again fighting the Monster Minds. Saw Boss orders his new weapon into the battle, Flap Jacks armed with thermal rays that cause the Lighting League's engines to overheat. The Lightning League are forced to retreat aboard the Pride.
Gillian suggests that they could use the cooling gem amethyst to shield their engines. There is a large source of amethyst on the planet Sandeen, the only cool planet in a desert galaxy and home of flying horces called Pegaceen and their riders. The Lightning League are unaware that Saw Boss has lured them into a trap on Sandeen.
Gillian constructs Fling Shot, a new vehicle which will be able to mine amethyst more quickly. The sensors detect what could be a powerful weapon in the city of Purple Home so they decide to land away from the city. However their mining operation is soon interrupted by Emperor Ramsey's troops flying Pegaceen. With the help of Antar and his Pegaceen riders they fight off Ramsey's troops.
Antar tells them that he was the democratic ruler of Sandeen before he was overthrown by a power hungry general called Ramsey who uses a powerful quartz micro-ray weapon to keep the population under control. Antar was imprisoned but was able to escape and on his way out of the city overheard Ramsey making a deal with Saw Boss to capture the Lightning League.
Jayce plans to distract the Monster Minds and Ramsey's forces while Antar leads his Pegaceen to fly over Ramsey's solar powered weapon and block out the light. Fling Shot lures the Monster Minds into position and when Antar's troops fly away from the weapon it fires and destroys the Monster Minds. With their allies beaten Ramsey's troops flee and the Emperor is captured.
Antar is once again the leader of his people and before they leave, the Lightning League help upgrade the micro-ray with solar storage to help protect Purple Home from the Monster Minds.