"Thunder Mountain" is the first of Tim Holt's 29 postwar westerns spread over the five year period from June, 1947 to June, 1952. While the film has one Zane Grey title, it has more elements in it from Grey's "To the Last Man" than from Grey's "Thunder Mountain", a not uncommon practice by RKO when dealing with the works of (Zane Grey). This one had Marvin Hayden(Tim Holt) returning to his Arizona ranch and finding it about to be sold for taxes. It has been in charge of his Mexican-Irish friend Chito Rafferty (Richard Martin). Local saloon-keeper Trimble Carson (Harry Woods), his friend Johnny Blue (Tom Keene) and Sheriff Bagley (Harry Harvey) have information that the ranch is to be the site of a dam and plot to obtain it. Plus, neighboring ranchers Ellen Jorth (Martha Hyer) and her brothers, Chick (Steve Brodie) and Lee (Robert Clarke), are antagonistic toward Hayden because of an old family feud between the Jorths and Haydens. Ellen and Hayden meet while looking for boundary markers between their lands and find stakes bearing the name of the water company. They conclude that Carson is trying to revive the old feud in hopes that one of the firey Jorths will kill Hayden. Later, Carson and Blue kill Chick by bashing his head with a rock so that Hayden, who is known not to carry a gun, will be charged with the murder. Hayden is jailed, but learns from family attorney Jim Gardner (Jason Robards Sr.), that there is still money in his ranch account that will pay the taxes, but the crooked sheriff stalls on accepting the payment. Chito and dance-hall girl Ginger Kelly (Virginia Owen) find evidence implicating Carson in the killing of Chick Jorth. Chito rescues Hayden from the jail, and they go after Carson and Blue. The latter are killed in a gun battle, the feud is settled and peace reigns as Hayden pairs off with Ellen, and Chito with Ginger.