Catherine Weldon is a widowed artist from New York who, in the 1880s, traveled alone to North Dakota to paint a portrait of Chief Sitting Bull. Her arrival at Standing Rock is met with open hostility by a US Army officer, who has stationed troops around the Lakota reservation to undermine Native American claims to the land. As Catherine and Sitting Bull grow closer, their friendship and his life are threatened by the government, and Catherine must stand up to fight for what is most important.