Riders of the Purple Sage tells the story of Jane Withersteen and her battle to overcome persecution by members of her polygamous Mormon fundamentalist church. A leader of the church, Elder Tull, wants to marry her. Withersteen gets help from a number of friends, including Bern Venters and Lassiter, a notorious gunman and killer of Mormons. She struggles with her "blindness" to the evil nature of her church and its leaders, and tries to keep Venters and Lassiter from killing the adversaries who are slowly ruining her.