The last place Lex Luthor expected his quest for the Black Lantern energy to take him was Arkham Asylum - specifically to the cell of The Joker! What clues about Lex's quest could The Joker have to offer, and why on Earth would Lex trust him? Get ready for a one-of-a-kind confrontation between comics' two greatest villains, as brought to you by the twisted minds of Paul Cornell and Pete Woods!