In 1867, two Union veterans and two Arapaho women they rescue from a Lakota war party set off on the Oregon Trail in search of a new beginning. Captain Caleb Stone and Sergeant Dil Smith find their plans to start over must change to include Little Rain and White Cloud, whose heritage poses obstacles to living among whites. The Trail tests them with storms, attacks by Indians and renegade whites, and the trials of travel. White Cloud's past catches up with her, endangering their lives. Finally, they reach their destination only to confront the greatest challenge yet: how to live together in a world where prejudice can be as powerful as a prairie twister.