2008: Deep in the Wyoming forest, Julian Cooke stumbles across the remains of a wagon. He's discovered what's left of the Preston Group, a convoy of settlers that vanished in 1856.
1856: as early snows descend, the wagon train are forced to dig in. They see the Native Americans also trapped nearby as their greatest threat, but they soon realise what true danger is after a woman is murdered. They must protect themselves against whatever is lurking in the woods, but perhaps their own terror will be just as dangerous.
Back in the present day, Cooke begins to question if the horror he is uncovering was in fact only the start of something much worse . . .