In an Elseworld where Supergirl was raised by Wonder Woman and Batgirl is a vigilante who keeps Gotham City safe from villainy, there could never be two more different super-heroines. But when the love of Supergirl's life is kidnapped by the Joker, the champions of Gotham and Metropolis must form a reluctant partnership. Back BlurbBatgirl, fierce protector of Gotham City, trusts no one...least of all super-powered crimefighters. Supergirl, protege of Metropolis magnate Lex Luthor and JLA member, trusts far too easily. When a kidnapping draws Supergirl to Gotham, the two heroes must save Lex Luthor from the clutches of the Joker... if they can find a way to work together. In this Elseworlds, Batgirl has gone to extreme measures to protect Gotham City, including banning paranormals and employing a surveillance system called Oracle. In Metropolis, the Justice Society is led by Wonder Woman, and funded by Lex Luthor, a pillar of society. Finally opening Gotham to Luthor and the Society, it goes wrong for Batgirl when the Joker kidnaps Lex. Supergirl charges back into Gotham to help find Lex, and what she and Batgirl find out together is the true nature of the man who has helped build Metropolis. — Description from Comic Vine community (comicvine.gamespot.com).
