Zero Hour

"Everything you know about the DC Universe is about to be affected. The universe will be shaken to its very foundations... and then rebuilt. In 1985, DC Comics dramatically altered comics' original universe with Crisis on Infinite Earths - an unforgettable, defining event in comics history that streamlined DCU continuity forever. Nine years later, the heroes of the DCU found the temporal fabric of their new reality unravelling and the biggest threat since the Crisis was about to be revealed." -- Page [4] of cover.