For years, Batman has been tracking a mystery. He's quietly been pulling a thread, conducting research in secret laboratories across the globe and stowing evidence deep in the Batcave, hidden even from his closest allies. Now, in an epic story spanning generations, the heroes and villains of the DC Universe, including Green Lantern, The Joker, Wonder Woman and more, are about to find out what he's discovered--and it could threaten the very existence of the Multiverse!