In the distant future, a genetic plague has separated humanity in two - Subterraneans who live in underground burrows to protect their health, and strong surface-dwelling Omniterraneans. Zuzan Cayan, a brilliant Subter girl with "light blindness," is about to leave the safety of her burrow and earn a living. With her low life expectancy, however, her options are slim. That is until she's offered the chance of a lifetime to study the population's broken genetic code, fix the divide and reunite the world once again.But when a new virus turns fatal for the Omnits, Zuzan must find a cure or humanity won't simply remain separate, it will become extinct. With enemies on all sides, Zuzan must hold on to the light at the end of the tunnel - or risk the world falling into darkness.