Evil is invisible, and it is everywhere. That is the only way to explain the series of misfortunes that have plagued the wagon train known as the Donner Party. Depleted rations, bitter quarrels, and the mysterious death of a little boy have driven the isolated travelers to the brink of madness. Though they dream of what awaits them in the West, long-buried secrets begin to emerge, and dissent among them escalates to the point of murder and chaos.

As members of the group begin to disappear, the survivors start to wonder if there really is something disturbing, and hungry, waiting for them in the mountains...and whether the evil that has unfolded around them may have in fact been growing within them all along.