"The world's first and greatest superheroes return! Or do they? A long-lost hero from the JSA crashes into our era with a grave warning...but it's too late. A mysterious and malevolent enemy has invaded the entire history of the JSA, and an all-new team must come together to defeat it. But what deadly secret does this messenger from beyond keep? Where are they from? And why is all of this happening now? Only the Time Masters know."-- Provided by publisher.