She thought of the horses, of the eyes in the earth. She thought about that number, 16. That strange number …

Near the dying English seaside town of Ilmarsh, local police detective Alec Nichols discovers 16 horses’ heads on a farm, each buried with a single eye facing the low winter sun. After forensic veterinarian Cooper Allen travels to the scene, the investigators soon uncover evidence of a chain of crimes in the community - disappearances, arson and mutilations - all culminating in the reveal of something deadly lurking in the ground itself.

In the dark days that follow, the town slips into panic and paranoia. Everything is not as it seems. Anyone could be a suspect. And as Cooper finds herself unable to leave town, Alec is stalked by an unseen threat. The two investigators race to uncover the truth behind these frightening and insidious mysteries - no matter the cost.