The Rainbow Trail, also known as The Desert Crucible, is Western author Zane Grey's sequel to Riders of the Purple Sage. Originally published under the title The Rainbow Trail in 1915, it was re-edited and re-released in recent years as The Desert Crucible with the original manuscript that Grey submitted to publishers.

The novel takes place ten years after events of Riders of the Purple Sage. The wall to Surprise Valley has broken, and Jane Withersteen is forced to choose between Lassiter's life and Fay Larkin's marriage to a Mormon.

Both novels are notable for their protagonists' mild opposition to Mormon polygamy, but in The Rainbow Trail this theme is treated more explicitly. The plots of both books revolve around the victimization of women in the Mormon culture: events in Riders of the Purple Sage are centered on the struggle of a Mormon woman who sacrifices her wealth and social status to avoid becoming a junior wife of the head of a local church, while The Rainbow Trail contrasts the older Mormons with the rising generation of Mormon women who will not tolerate polygamy and Mormon men who do not seek it.

The novel is the basis of a 1931 film of the same name. Frank McGrath, later of Wagon Train, made his acting debut in this film though his role is uncredited. (wikipedia.org)