Canadian Mountie O'Rourke (Alan Ladd) and his Cree companion, Cajou (Jay Silverheels), come upon the scorched remains of a wagon train and find beautiful lone survivor Grace (Shelley Winters), who claims the attack was carried out by American Indians. Realizing the attack is only the beginning, the men fear war between the American Sioux, the Canadian Cree and the whites. O'Rourke must now protect his troops from further attack and save Grace from being extradited to Montana on a murder charge.