Fred C. Dobbs and Bob Curtin, both down on their luck in Tampico, Mexico in 1925, meet up with a grizzled prospector named Howard and decide to join with him in search of gold in the wilds of central Mexico. Through enormous difficulties, they eventually succeed in finding gold, but bandits, the elements, and most especially greed threaten to turn their success into disaster.

A small-town doctor learns that the population of his community is being replaced by emotionless alien duplicates.

McCord’s gang robs the stage carrying money to pay Indians for their land, and the notorious outlaw “The Oklahoma Kid” Jim Kincaid takes the money from McCord. McCord stakes a “sooner” claim on land which is to be used for a new town; in exchange for giving it up he gets control of gambling and saloons. When Kincaid’s father runs for mayor, McCord incites a mob to lynch the old man whom McCord has already framed for murder.