The Joker will go to any lengths to get Harley Quinn back after she is abducted by a strange culprit. But who? Mysterious, Joker-like monsters are stalking the streets of Gotham City, collecting severed heads. But why? Jim Gordon is missing, and after receiving a package containing a bloody piece of Gotham City's commissioner, Batman knows he must be willing to do anything to save him. But how? When The Joker proposes an uneasy alliance with Batman, the answers to those questions begin to become clear-and they will shake Gotham City and the Bat-Family to their core.