"The Joker has been murdered. His killer is a mystery. Batman is the World's Greatest Detective. But what happens when the person he is searching for is the man staring back at him in the mirror? With no memory of the events of the previous night, Batman is going to need some help. So who better to set him straight than John Constantine? The problem with that is as much as John loves a good mystery, he loves messing with people's heads even more....