A month after the Justice League of America first forms, Lex Luthor sends out an ultimate killing machine out to destroy the League's leader and Luthor's archenemy, Superman; John Corben, now a cyborg known as Metallo, whose body is created out of Superman's weakness, Kryptonite. But with little help from the Justice League, how can Superman survive Metallo's Kryptonite attacks and save his hometown Metropolis? His answer...another survivor of his home planet Krypton; Kara Zor-El, AKA Supergirl! Can Superman and his cousin work together to defeat Metallo and defend Metropolis?
