2008: Deep in the mountain forests of Wyoming, Julian Cooke stumbles across the rotting remains of a wooden wagon. He's discovered what's left of the Preston Group, a convoy of settlers that vanished in the winter of 1856. It's clear that something horrific happened here all those years ago, but Cooke can only find a few tantalising clues. 1856: As early snows descend, the eclectic group of settlers that form the Preston wagon train are forced to dig in. Miles from any kind of civilisation, they see the group of Native Americans also trapped nearby as their greatest threat. But they soon realise what true danger is. When a woman is found murdered, one of the Indian party struggles wounded back to camp, whispering of unspeakable evil as he dies. United by fear, the settlers and the Indians must protect themselves against whatever is lurking in the woods. But as suspicion and panic grow, perhaps their own terror will be just as dangerous. Or maybe, whatever's out there is worse than anything they can imagine. Back in the present day, as Cooke unravels the mystery, he must question if the horror he is uncovering was in fact only the start of something much worse...