When the villainous Crime Syndicate of Amerika and a mysterious dark energy attack our world, the Justice League of America is immediately put on the defensive. But as the JLA locks horns with their new otherworldly rivals, Dr. Impossible calls forth the Omega Man, a terrifying alien entity capable of destroying not only the Justice League, but the Earth itself. With the coming of the Omega Man, members of both the JLA and the CSA must choose sides, as the fate of the planet hangs in the balance. As alliances and friendships are forged and destroyed, can the remaining superpowers unite long enough to put a stop to the Omega Man's rampage?