When the charred remains of a local farmer are discovered in his locked bedroom—untouched by external flames, yet burned from the inside out—Detective Inspector Keith Tremayne faces a mystery defying rational explanation.

The English countryside’s tranquility shatters as more victims appear: a schoolteacher in her garden, a vicar in his church study, a teenager in a locked bathroom. Each body bears the impossible hallmarks of spontaneous human combustion—a phenomenon dismissed by science yet eerily consistent with each death.

DI Tremayne—a hardened investigator more comfortable with racing forms than academic theories—reluctantly teams with his methodical partner, Sergeant Clare Yarwood. While Tremayne clings to conventional explanations, Yarwood uncovers disturbing connections between victims and ancient pagan sites scattered throughout the region.

Their investigation reveals a shadowy cult operating beneath respectable village life. Its members—doctors, teachers, and local officials—gather under moonlight to perform centuries-old rituals, invoking forces they neither understand nor control. The deaths aren’t random accidents but calculated sacrifices feeding something awakening in the dark.

Each night, the boundary between criminal investigation and supernatural threat blurs. Tremayne’s stubborn rationality becomes his greatest strength and potentially fatal weakness as he confronts adversaries wielding weapons beyond fingerprints and forensics.