On a mission to the last surviving outpost of Krypton, Superman learns how Brainiac 5's ancestor was the one who participated in the destruction of his homeworld.

The Legion must face Imperiex in final battle... while a traitor lurks in their midst.

After eliminating Imperiex, Brainiac 5 takes over his army and plans to conquer the universe. With Superman presumed dead, the other Legionnaires must stop him before it is too late.