In 1864 Cavalry Captain John Hayes reluctantly follows orders to become the civilian boss of the Overland Stage Line, which keeps the flow of Western gold to the Union and will help it win the Civil War. Headquarters for the stage line is a small Colorado town with Southern sympathizers who will do anything they can to sabotage his mission. Resistance to his efforts is led by former friend ad colleague Clay Putnam, who has taken advantage of Hayes' absence and married his former sweetheart.