Three years ago, the gray fell and the Ashen hunted every living thing. Elena, a former ER doctor, built the "Lighthouse" shelter in the ruins and rescued Mia, a six-year-old girl wearing a silver pendant. When she unearthed her father's old storage drive, she discovered the gray was no natural disaster—it was a man-made weapon experiment, and her father was one of its creators. Elena herself is "Patient Zero," the only antibody that can end the apocalypse. The termination code is hidden inside Mia's pendant. Facing a betraying partner, a rival with opposing ideals, and the shadow organization "the Black Tower," Elena must face the truth: the one who ends the gray can only, and must only, be herself.
