The unscrupulous attempts by speculators Dr. West and Jim Prince to have a railroad pass through lower California are met with opposition by Spanish landowners led by Dona Maria Saltonstall, who tries flirting with West to restore their property. Pereo, a religious fanatic who works for Dona Maria, believes in the curse of the Gray Wolf's Ghost: if a member of Dona Maria's family mates with an alien, fortune and life will be lost. Meanwhile, West's son Harry, whom he deserted years before, comes to avenge the wrong done to his mother.