Twelve-year-old Simon Barnacle is falling apart. Literally. His body is turning to ash. On top of that, his father has died, the crops have rotted, bog pox has infected nearly everyone he knows, and strange whispers of “ignis fatuus” rustle through the trees. After his mother falls ill, Simon travels to the village to find help. Along the way, he’s captured and imprisoned at Bog’s End by the Wickfields, a dastardly pair of siblings who have ruled the Marshlands since its inception. Simon learns the land and its workers have become imbalanced after dark energy was leaked from an underground chamber ruled by a terrifying creature, Balterax. The consequences are dire; the land and all its inhabitants will soon be destroyed, crushed between two opposing worlds that are in a violent tug of war for energy. The Wickfields convince Simon they will transition him and his mother to the new harvest world if he retrieves dark matter from the chamber. Simon is terrified of what lurks in the dark, but with his mother near death and his body parts starting to fall off, he knows it's either face his fear or face certain death.