Famed frontiersman Jim Beckwourth, a former slave and adopted member of the Crow tribe, has lived a life of unparalleled adventure as a trapper and mountain man. For years, he has moved between cultures and among the Indigenous people of the western frontier. In the late 1830s, Beckwourth goes to work as a trader for Andrew Sublette. Uncommonly brave, he crosses the mountains, bartering and trading among the Cheyenne and other western tribes. By the time America goes to war with Mexico, there are few that possess his knowledge of the frontier and its native inhabitants. Eager to serve his country, Beckwourth becomes a dispatch rider on the Santa Fe Trail, facing peril at the hands of the Comanche and Pawnee. Threatened by the encroachment of soldiers and settlers, the tribes are determined to protect their homelands. While escorting a greenhorn down the trail, Beckwourth risks his life to carry his dispatches and save his young companion during a deadly showdown with the Pawnee.