It is 1879. Coffey (Karl Geary), a young Irishman settled on the plains of Dakota, is about to ask his sweetheart to marry him. His dream of wedded bliss is shattered, however, when something or someone attacks the young lady's family farm, kidnapping the women and children and slaughtering the men. Coffey joins a group of local ranchers and cavalrymen in search of the victims, who are assumed to be prisoners of a fierce band of natives.
Put off by the sadistic and single-minded tactics of self-appointed group leader Henry Victor (Doug Hutchison), Coffey sets out with a couple of ranchers (William Mapother and Highlander's Clancy Brown), as well as a teenaged boy and a freed slave (Sean Patrick Thomas). They soon discover mysterious holes in the ground and a catatonic girl buried in the dirt, suggesting that they may not be hunting an ordinary tribe. A sinister enemy seems to be stalking them from below the serene grassy plains of the vast new frontier.