In the early 1900s, Wes Anderson is arrested for "moonlighting," a term the locals use for nighttime cattle rustling. Outraged by Wes's crimes, a mob led by rancher baron Alex Prince and his men, refuse to wait for the trial and storm the jail. They seize the hobo Tidy, mistaking him for Wes, and hang him and throw his body in the river. The uproar gives Wes an opportunity to escape, but as he witnesses the senseless killing of the amiable Tidy, he swears revenge. Later, Rela, Wes's former sweetheart, comes to claim his body, and is told a story by Clem Usqubaugh, the undertaker: After the lynching, a mysterious man, claiming to be a relative of Wes, arranges for an expensive funeral for the deceased. At the funeral, the man delivers a eulogy, describing the dead man as a wanderer who was basically good, but discontent with his lack of money. After warning that the ghost of the dead man may seek revenge on the lynchers, he robs the men in attendance, pays the undertaker's bill with the stolen money and escapes. After the undertaker then explains to Rela that the man has not been seen since, she returns home to Rio Hondo and reports to Wes's younger brother Tom, with whom she is now romantically involved, that Wes is still alive. Meanwhile, the vengeful Wes sets fire to Prince's barn, and lassoes and drags to death the mob ringleaders who were instrumental in Tidy's lynching. In a gunfight with two of Prince's men, Wes is shot in the shoulder, so he returns to his mother's house, where he has not been for five years, to hide until he recuperates. Although he had hoped to renew his romance with Rela, she refuses to see him. However, when Wes is lured out of the house by a bobcat threatening the ranch animals, he runs into the self-sufficient Rela, who is also tracking the cat. Although Rela still loves Wes, she has decided on a life with Tom and makes Wes promise not to ruin their plans. In Rio Hondo, at the bank where he works, Tom, who is distracted by Wes's secret reappearance, makes mistakes and is dismissed by the bank president, Mr. Mott. On his way home, Tom is followed by Wes's friend, the outlaw Cole Gardner. Cole is welcomed at the Anderson house after Wes recognizes him, and Cole later convinces Wes to join him in a robbery of the Rio Hondo bank. Because Tom is troubled by his dismissal and has always secretly admired Wes, when he overhears the plans, he decides to join them. Although Wes tries to dissuade him from the outlaw life, Tom argues that he wants the money to marry Rela. During the night, Wes slips out to Rela's ranch and warns her that Tom has gotten the same wandering "bug" that bit him. Wes again tries to renew their romance, but the angry Rela sends him away and warns that if anything happens to Tom, she will hold Wes responsible. On the morning of the holdup, Cole, Wes and Tom enter the bank and take the money. However, as they leave, Mott shoots Tom dead, and Wes and Cole escape in Mott's horseless carriage. Soon a posse is sworn in and begins a search for the two outlaws. Rela convinces the sheriff to deputize her and, as she promised Wes, begins her own search for him. At the hideout, which is concealed by a huge waterfall, Cole doublecrosses Wes and escapes with all the stolen money, leaving him unconscious and tied up. Cole soon encounters Rela and shoots at her, but Rela kills him in the resulting gunfight, then retrieves the stolen money and resumes her search for Wes. She finds him at the cabin and after untying him, takes him at gunpoint toward town. While they are crossing the waterfall, she slips and nearly drowns. Instead of abandoning Rela to make his escape, Wes climbs down and rescues her. At the cabin where Wes treats her injured leg, Rela confides that, while she was drowning, she realized that she drove Wes to moonlighting five years ago with her need for a "perfect relationship." When she admits that she still loves him, Wes tells her that he has decided to turn himself in and asks her to wait for him while he serves his prison sentence. The next day, they cross the waterfall and head for town.