Before dying, Ned Glaze, a wizened old convict, tells his young cellmate, Joe Mundy, the hidden location of the $250,000 in gold he stole from the railroad thirty-five years earlier. Once released from prison, Joe boards a bus that crosses Hoover Dam to reach its destination: Glendale, Arizona. Unknown to Joe, he being stalked by a sinister, hulking man. In Glendale, Joe enters the City Pig diner, where no-nonsense, gum-chewing waitress Henrietta "Hank" Clifford objects to his demanding demeanor. After becoming drunk, Joe refuses to leave the diner until its owner, Mr. Ding, comes to close down for the night. As Hank walks home, she finds Joe lying unconscious in the road, a victim of a mugging. Hank drives Joe to the Glendale hospital, where Marshal Hannibal comes to question him. After the hospital treats Joe, Hank takes him to the boardinghouse where she lives and works as a waitress and introduces him to its proprietors, the addled Mrs. Williams and her unctuous son Clem. The next morning, Clem and his younger brother, Little Brother, the man who tailed Joe from prison, follow Joe as he heads out of town to the ranch owned by their crazy uncle George. Popping up from beneath some railroad ties, Uncle George stones Joe off his property as Little Brother tells Clem that he failed to find the treasure map after mugging Joe the previous night. In Glendale, the marshal summons Joe to his office and, after perusing his prison record, offers to help him go straight. The marshal then mentions that Ned, his ex-cellmate, was one of the last western bandits who stole a large sum of money in a railroad robbery. Before he could be proved guilty, however, Ned was arrested for stabbing a man to death. That night, Hank sees Joe on the pier near the diner and joins him. When Joe makes fun of her ratty, cheap shoes, Hank retorts that one day she will be rich and own shoes with diamond buckles. As Joe and Hank return to the boardinghouse, the eccentric Williams family fantasizes about spending their riches. The next day, the marshal gives Joe a lead about a job at the Sid Songster Wrecking Company, and when Joe goes there, he hears a call over the police radio, requesting a wrecker to haul a trailer that plunged into the lake. Sid, Jr., the owner's son, is reluctant to compete for the job with the more established Brokaw company, but Joe convinces him to drive to the lake. As the whole town watches, Joe plunges into the water, and upon ascertaining that a small dog is trapped in the trailer, risks his own life to save the canine. Impressed, Sid, Sr. hires Joe and the marshal promises to issue him a valid driver's license. As Joe looks up, he sees Mr. Ding and Hank beaming approvingly at him. The following evening, Hank dons a pair of shiny new shoes and accompanies Joe to the lake for a boat ride. After they row out into the water, Hank proudly shows Joe her shoes. When thunder begins to rumble in the background, lightning illuminates the night sky and Joe spots Little Brother watching him from a boat in the distance. Upon returning home, Clem insists that Joe accompany him to his basement office, where the whole family is assembled. Clem then explains that Ned murdered Clem's father, his partner in the robbery, and therefore the gold is the Williamses' family legacy. When Joe rejects Clem's offer of one-fifth of the treasure for showing them the way to the gold, Clem warns that the family will relentlessly hound him. When Joe returns to his room, Hank is waiting there for him and he assumes that she is in league with the Williamses. After Hank protests her loyalty to him, Joe tells her that he was unjustly convicted of manslaughter and then asks her to join him on his treasure hunt, promising to buy her diamond-studded shoes. To confound the Williamses, Hank uses her life savings to buy a jeep in which they will carry the gold. She then hides the vehicle in a garage next to the diner, waiting for the day of the big horse race which the entire town, including the Williams family, plans to attend. After making certain that Uncle George and the others are in the stands, Joe and Hank drive the jeep to Uncle George's ranch, the starting point of the treasure map. Unseen by them, the marshal follows, but his car is soon disabled by the rugged terrain. While careening down a treacherous, rocky cliff, Joe is thrown from the jeep and Hank runs to his aid. As they drag the jeep uphill through some dense underbrush, they are shocked to find the Williams family waiting for them. After Clem threatens Hank's life, Joe lays out the trail that passes along the cliff of caves leading to the fingers of black lava in which the gold is buried. The marshal, continuing on foot, finds Joe's abandoned jeep and drives on until he spots the Williamses' station wagon. Upon reaching the site of the lava flow, they discover that it has been flooded by the Hoover Dam and is now part of Lake Mead. As Clem sinks into the water in shock, Little Brother threatens Joe with his shotgun. After knocking the gun from Little Brother's hand, Hank scuffles with Ma while Little Brother threatens Joe with a pickax. Just then, the marshal appears, shoots Little Brother in the wrist and then sends the Williams family home. When they leave, he muses that they will continue their search, never to accept that the pot of gold just does not exist. After Hank declares that she and Joe really had no right to the gold, Joe, disappointed, begins to trek up the hill. When Hank stumbles and falls, Joe rushes to her side, picks her up and carries her, causing the marshal to smile.