A Cambridge historian dies under suspicious circumstances, leaving behind the nearly completed manuscript of a book on the alchemical experiments of Isaac Newton. Her son, a research scientist, hires his former lover, Lydia, to finish the book. Meanwhile, a shadowy group of animal-rights activists escalate their violent attacks. As Lydia is drawn further into Newton’s seventeenth-century world, she begins to believe that his ghost is haunting her and, perhaps, directing the murderous events of the present.