In a post-apocalyptic world, Rachel Wheeler is caught between who she is and who she's becoming. A bizarre mutation has her humanity hanging by a thread, especially when the Zaphead inside her wants to kill her friends and lover. As the mutant Zapheads form a social order and shape a new world in the wake of catastrophic solar storms, the few remaining humans band together in a struggle for survival. But not everyone shares the same goal: a rogue military unit plans to attack the mutant settlement while Rachel's group seeks a remote, peaceful life beyond their notice. And the Zapheads have a special role for her that could save the human race at the cost of her own identity. Torn between two possible futures, will Rachel sacrifice herself to prevent the extinction of her kind?