Star Boy's home planet Xanthu is attacked by the Khunds, and the Legionnaire must join with his old teammates—the Uncanny Amazers—to save their world!

Star Boy and Monstress return to their homeworld of Xanthu after a communications blackout. While the rest of the galaxy has written it off as standard Xanthu failure from being a border world, the Legionnaires quickly discover that Xanthu is in fact in the middle of an invasion. Teaming with the Uncanny Amazers, specifically Kid Quantum II, the Legionnaires help protect the innocent and get to the bottom of the invasive forces just as a group of Khunds swoop in to take the glory of victory. Suspicious of the Khunds, Star Boy and Monstress resolve to investigate and Star Boy inadvertently invites Kid Quantum to the Legion - which she surprisingly accepts after previously condemning the team.