Barry uses his time travel power to change past events. However, when he tries to save his family, he involuntarily changes the future. Barry becomes a prisoner of a reality where General Zod returns and threatens universal destruction. In this world, however, there are no superheroes to turn to. Unless Barry convinces a completely different Batman to come out of retirement and save an imprisoned Superman, also not the one he expects. Barry's only hope of saving the world he lives in and returning to the future he knows is in the race for his life. But will the final sacrifice be enough to restore the old course of events?