In a lonely village in the Peak District, during the onset of a once-in-a-lifetime snow storm, Constable Ellie Cheetham finds a body. The man, a local ne'er-do-well, appears to have died in a tragic accident: he drank too much and froze to death. But the facts don't add up: the dead man is clutching a knife in one hand, and there's evidence he was hiding from someone. Stranger still, an odd mark has been drawn onto a stone beside his body. The next victims are two families on the outskirts of town. As the storm rises and the body count grows, Ellie realises she has a terrifying problem on her hands: someone - or some thing - is killing indiscriminately, using the storm for cover. The killer is circling ever closer to the village. The storm's getting worse. . .and the power's just gone out.