The events depicted in Riders of the Purple Sage occur in mid-spring and late summer 1871. Early in Riders of the Purple Sage , Jane Withersteen's main conflict is her right to befriend a Gentile. (The word Gentile means "non-Mormon" and is used a lot in the book). Jane Withersteen’s father wished Jane to marry Elder Tull, but Jane refused saying she did not love him, causing controversy and leading to persecution by the local Mormons.
Jane’s friend, (cowboy) Bern Venters is "arrested" by Tull and his men, but is not clear under what authority. Jane defends Venters, declaring him her best rider. Her churchmen refuse to value the opinion of a woman:
"Tull lifted a shaking finger toward her. 'That'll do from you. Understand, you'll not be allowed to hold this boy [Venters] to a friendship that's offensive to your bishop. Jane Withersteen, your father left you wealth and power. It has turned your head. You haven't yet come to see the place of Mormon women ...'"
It is here we first hear of Lassiter. Ironically, at the moment when Venters mentions Lassiter’s name, the actual Lassiter is seen approaching in the distance by Tull’s men.
Upon his arrival, Lassiter expresses his trust in the word of women, at which Tull rebukes him, telling him not to meddle in Mormon affairs. Tull’s men begin to take Venters away, and Venters realizes who he is and screams "Lassiter!" Tull understands that this is the infamous Lassiter and flees.
Lassiter inquires as to the location of Millie Erne's grave, to which a transfixed Jane agrees to take him. Venters later tells Jane he must leave her. When she protests, Venters delivers this statement: " ... Tull is implacable. You ought to see from his intention today that ... but you can't see. Your blindness ... your damned religion! Jane, forgive me ... I'm sore within and something rankles. Well, I fear that invisible hand [of Mormon power in the region] will turn its hidden work to your ruin.", showing that Venters could see far into the future, and although Jane rebukes his statement, he is indeed correct.
Jane’s red herd is rustled shortly afterward and Venters tracks it and returns it to Jane. Bern finds the herd, but, in his travels, wages a gun battle with two of Oldring’s rustlers, killing one and managing to wound Oldring’s notorious Masked Rider. Upon further examination, he removes the maskand shirt of the wounded rider and learns that the Masked Rider is a young woman named Bess whom he believes had been abused by Oldring. Venters experiences a large amount of guilt about shooting a girl and decides that it is his duty to save her.
Venters discovers Surprise Valley and Balancing Rock, where he takes Bess, the girl he has found. Bess gradually gains health and begins to fall in love with Venters who begins to fall in love with Bess. Each explain their individual stories ambiguously, but through Venters' dedicated care for Bess, the pair forms a mutual love that leads to their resolve to marry. Bess also discovered the truth concerning Oldring’s rustlers, who rustled cattle only to disguise their true lifestyle of surviving off gold in the streams and business deals with the Mormons.
Venters then determines that there is a need for supplies warranting a trip back to Cottonwoods. On his way, Venters sees Jane Withersteen’s prize horses being stolen. He kills the thieves and retrieves the horses for Jane, but unfortunately loses his horse, Wrangle.
Jane’s horses are returned to her, and are locked in the entry hall to Withersteen's house. Venters officially breaks his friendship with Jane at this time. He goes into the village and proclaimed that he was breaking his friendship and leaving. After he leaves, Jane’s other herd gets stolen.
Jane at first pretends to love Lassiter— knowing he came to Utah to avenge his sister Milly Erne — to prevent him from murdering Mormon elders she knew were guilty. The two characters grow to love each other. Then Jane's adopted daughter Fay is kidnapped and Lassiter kills Bishop Dyer while risking his own life.
The four main characters— Venters, Bess, Lassiter, and Jane — realize that they can no longer safely stay in Utah. Lassiter convinces Jane to prepare to leave with him, Lassiter determines the name of a Mormon who contributed to the ruin of Milly and Jane implicates her father in the proselytizing of Milly. In a stateof shock, Jane packs.
Meanwhile, in Surprise Valley, Venters and Bess are preparing to leave as Jane and Lassiter departing, except on burros. Lassiter sets fire to Withersteen House and flees on horseback with Jane. They encounter Venters and Bess in travel. Before they part, Lassiter explains that Bess is not really Bess Oldring, but actually Elizabeth Erne, the lost daughter of Milly Erne.
Jane gives Venters her horses, Venters and Bess gallop for Venters' Illinois home, and Lassiter and Jane find refuge in Venters' valley paradise. On the way, Lassiter rescues Fay, but they are pursued to Surprise Valley. As Tull and his men begin to climb up the cliffside, Jane shouts to Lassiter to "roll the stone," which he does. The ensuing avalanche closes the outlet to Deception Pass "forever." (This is, of course, not true, as Jane, Lassiter, and Fay return in Grey's sequel, The Rainbow Trail/The Desert Crucible .)
Unlike many Western novels, which are often straightforward and stylized morality tales, Riders of the Purple Sage is a long novel with a complex plot that develops in many threads. The story is set in the cañon country of southern Utah in 1871. Jane Withersteen, a Mormon-born spinster of 28, has inherited a valuable ranch and spring from her father, which is coveted by other Mormons in the community. When Jane refuses to marry one of the (polygamous) Mormon elders and instead befriends Venters, a young Gentile rider, the Mormons begin to persecute her openly. Meanwhile, Lassiter, a notorious gunman, arrives at the Withersteen ranch in search of the grave of his long-lost sister, and stays on as Jane's defender while Venters is on the trail of a gang of rustlers that includes a mysterious Masked Rider. Jane is intent on preventing Lassiter from doing further violence to Mormons and is eventually driven off her ranch as the persecution escalates, but she and Lassiter fall in love, Lassiter solves the mystery of his sister's death and the fate of her child, the Masked Rider is unmasked, and Venters finds his own romance. Along the way, Jane also finds time to adopt Fay Larkin, a young Gentile orphan who accompanies her and Lassiter at the end of the story
Riders of the Purple Sage was written in 1912 and is set in a remote part of Utah after the influx of Mormon settlers (1847-1857) as a backdrop for the plot (1871). The Mormons had been centered in Kirtland, Ohio in the 1830s and Zane Grey would have been aware of the Mormon sect given that he grew up in Zanesville, Ohio.
Plural marriage was only officially prohibited by the Mormons with the issuing of the First and Second Manifesto in 1890 and 1904 respectively, enacted primarily to allow the territory to attain statehood. In 1871, mainstream American society found plural marriage offensive. Even after the Morrill Anti-Bigamy Act was passed in 1862, the practice continued. Therefore, Zane Grey described the distaste of the institution through Lassiter in 1912, some 22 years after the practice had officially ended.