As Ray Palmer considers whether to reveal his secret identity of The Atom to his fiance Jean Loring, a second moon appears in the sky, signaling the start of the League's latest crisis. He and the other Leaguers meet in their satellite HQ and split up into teams, tackling the environmental disasters that are caused by the second moon's appearance, unaware that aliens are watching their actions. After the aliens attack the League, the heroes discover that they are inhabitants of a planet whose moon has appeared above Earth.They pretend to surrender only to lure the Leaguers to their planet and attack them, planning to wipe out the entirety of the human race, believing that humanity is as warlike as themselves. The League defeats them and sends the alien planet and its moon into the far future where they will do no harm.