The worst of her nightmares has finally come to pass: Raggy Maggy is thrown into the depths of the Pits, an underground labyrinth of caves filled with Rotters, lost Meridians, and forgotten Moon Children. Her allies promised they would come for her, but once the darkness closes in, it's hard to believe she will ever see a brighter future. Injured and desperate, Maggy follows the plan to uncover the true origins of the Rot, a plague that keeps the city of BrightStone under Meridion's thumb. But when she's welcomed into a village of Meridian scientists, charged with finding a cure, she wonders if once again, the truth is not what it seems. There are sinister things happening both above and below, and they may lead Maggy to unlock the secrets of her iron heart—and quite possibly, the very secret of Meridion itself.