In colonial America during 1763, Martin Garth, a powerful trader played by Howard Da Silva, attempts to protect his own interests by secretly supplying guns to the Indians in order to halt the westward expansion of settlers. Garth tries to buy a young British indentured servant, Abby Hale, played by Paulette Goddard, but is outbid by Virginia patriot Capt. Christopher Holden, played by Gary Cooper, who frees her. In an effort to drive white settlers out of the region, Garth instigates an Indian rebellion against Fort Pitt, led by Chief Guyasuta, played by Boris Karloff. Jealous of Abby, Garth's wife, Hannah, played by Katherine DeMille, plots to have her captured by the Indians. Holden saves Abby just in time from being tortured to death by Guyasuta. Upon returning to Fort Pitt, they find it under attack by Indians, but Holden manages to save the fort and its inhabitants by obtaining reinforcements. He then kills Garth in the fort's stable before being reunited with Abby permanently.