The Dark Knight and the Clown Prince of Crime's alliance started off shaky, but now it seems to have shattered entirely. Batman has imprisoned The Joker in the Batcave, desperate to find answers about both the disappearance of Jim Gordon and the strange, genetically modified humanoid monsters gathering severed heads across Gotham. But when one of these monsters' tissue samples comes to life, Batman comes face-to-face with a creature even the World's Greatest Detective doesn't fully understand, and he may have no choice but to resume his partnership with his greatest enemy.