A decade ago, a terrible disaster fell on the small, remote town of Indigo Falls, forcing the residents deep underground due to the searing pain of sunlight touching their skin. Dr. Imogen Moran has become the town's charismatic leader, giving the people rules to always live by in the "belowground"--always tell the truth, avoid the sunlight, never touch skin to skin. The last one, the one at the end of the list, is about to be broken--never, never go outside.