When future humans imagined the world, they probably didn't see horse drawn carriages. But for earth, that's reality. Years ago the aliens took over, ruled the world, and then finally were defeated by a group of superheroes. Superheroes who are now dead. Because the citizens they once tried to save turned against them. Cala vows to become the next hero, and avoid the mistakes of the ones in the past. She enlists herself to the king, and joins a secret resistance. But not everything is as it seems, and Cala soon learns that heroes can be replaced.