Rainbow Trail, The The. Zane Grey

Ten years after the events of Riders of the Purple Sage, John Shefford, a disillusioned preacher from Illinois travels to Arizona and takes refuge in a village controlled by polygamist Mormons hiding from the federal government. It's there Shefford learns the story of Fay Larkin: years ago, the infant Fay, along with Jane Withersteen and a gunslinger known as Lassiter, were trapped in Surprise Valley. Intrigued, Shefford decides to track Fay down.