After the disastrous events of the Justice League Annual, Martian Manhunter decides to take matters into his own hands and negotiate a peace with Legion of Doom leader Lex Luthor. Traveling to a distant moon, the two enemies face their intertwined pasts in a showdown for the fate of the Multiverse. However, before either of them can lay claim to the power of the Source Wall once and for all, an unexpected threat forces them to unite…or risk death at the ends of the cosmos.