The Great Sioux Uprising.

During the Civil War, in Wyoming, horse dealers Joan Britton and Stephen Cook are competing to supply the Union Army with horses. A Cherokee is in the area to stir up the Sioux against the Union just as Cook decides to steal a herd of Sioux horses. Ex-army doctor Jonathan Westgate opposes Cook’s unscrupulous methods as well as being Cook’s rival for the affections of Joan. It seems Westgate is the only one able to prevent a new Indian war.