Act I

Reluctant gunfighter and ex-marshal Bert McGraw returns to the dangerous frontier town Rio Hondo to see his ailing brother. Dropping by the saloon to make amends with an ex-girlfriend, Rosarita, he runs into nemesis— and newly hired marshal— Sanchez. The trigger-happy bandito challenges the reticent McGraw, but he demurs, accidentally murdering one of Sanchezʼs men in the process.

When Bert reaches the family ranch, The Double-B, his sister-in-law Clementine informs him of his brotherʼs passing, and of Sanchez and the coming railroadʼs plans to take the ranch. In soliciting his help to save the home she loves so much, a flashback is triggered where Bert confronts the tragedy that made him quit marshaling in the first place: his accidental shooting of a small boy during a bank robbery. Before Clem can convince Bert to help her, Sanchez arrives to arrest him. In the ensuing gunfight, Bert and Clem— and ranch hands Flapjack and Ding-Ding— fend off the invaders, forcing Bertʼs hand to aid in the fight.

In town, Sanchez and railroad representative Cole agree to put pressure on The Double-B by hiring renowned killer Eudora Cummings. Back at the ranch, Clementineʼs blind sister, Iris, arrives with a posse of aspiring gunfighters. Unfortunately, despite her reputation as the finest blind gunfighter in the West, it becomes clear that she can no longer effectively fire a gun, since sheʼs, you know, blind.

While preparing The Double-B for the next attack, Iris is confronted by the woman who blinded her: Eudora. After Iris guns her down in a duel, she is immediately shot by a member of Sanchezʼs gang lying in wait, igniting a massive gunfight killing much of the Sanchez gang and Irisʼ young sharpshooters. End Act I.

Act II

The bloodshed proves too much for Bert, and he abandons Clem. Back at the saloon, when Cole declares he wants to settle with Clementine, Sanchez shoots him dead and, in the course of the conversation, announces heʼs acquired a Gatling gun to be delivered that afternoon. A horrified Rosarita sneaks away.

Outside town, Bert is getting drunk in a saloon when Rosarita arrives to warn him about the Gatling gun. Bert still blames himself for that slain boy so many years ago, until Rosarita— in flashback form— reveals the truth: it was Sanchez! Sanchez murdered that boy, framing Bert in the process. Reassured, our hero resolves to intercept the Gatling gun and save the day.

While Sanchez, reinforced with a new group of killers, lays siege to the McGraw ranch, Bert captures the coach with the Gatling gun, then confronts his nemesis, killing his gang. Sanchez gets away, but Bert follows the bandito to an abandoned mineshaft with Clementine trailing close behind.

In the mine, Bert has Sanchez cornered until a cave-in gives his enemy the upper-hand. Freeing herself from the rubble, Clementine shoots Sanchez at the last second. Bert returns Clem to the Ranch and says goodbye, riding off into the sunset.