At Camp Mercury in the Nevada desert, scientists and soldiers prepare for an atomic bomb test, which is to take place early the following morning. While waiting for the blast, reporter Larry Fleming is reassigned to a breaking story at the Carson City penitentiary, from which convicts Sam Hurley and Bart Moore have just escaped. On the way there, Larry stops at a diner and gives stranded dancer Dorothy "Dottie" Vail a lift. Sam and the wounded Bart, meanwhile, meet fellow gang member Dummy, who is waiting for them in a car on another stretch of the highway. Later, Sam confronts a gas station proprietor at gunpoint, and when the man attempts to disarm him, shoots him. Sam and Bart, who are to rendezvous with another cohort, Johnny, and collect some hidden loot, then change into clothes provided by Dummy and junk their car. Soon after, a car pulls up to the station, and Sam, Bart and Dummy force their way in, to the shock of driver Kay Garven and her lover, Arthur Ashton. Sam, who has promised to find Bart a doctor, orders Kay to drive and, in the backseat, finds a letter addressed to Kay and her husband, Dr. Neal Garven. While stopped at a diner, Sam calls Neal at his Pasadena office and tells him that if he wants to see his wife alive, he should hurry to the desert with his medical gear. Soon after, Kay's car runs out of gas, and Kay flags down the next passing car--Larry's. As before, Sam pulls a gun on Larry, and he, Kay, Arthur, Burt and Dummy pile into Larry's station wagon with Dottie. Upon arriving in Lost Hope City, a ghost mining town within the atomic bomb test range, Sam tells Kay about his phone call to Neal. With a frightened laugh, Kay reveals that she is divorcing Neal and doubts whether he will bother to come. Later, while alone in one of deserted houses, Kay admits to Arthur that she is attracted to Sam. Larry and Sam, meanwhile, talk about Sam's heroics during the war. The embittered Sam feels no remorse for his "illegal" murders and declares himself just another victim of the war. The group then is joined by Asa Tremaine, an old prospector who has just come down from the hills. Disturbed by Asa's appearance, Sam leaves to scout the town and discovers that the gas tank on Larry's car is leaking. Upon returning, Sam demands that Kay go to the kitchen with him, and Arthur, fearing for her safety, angrily protests. Sam guns Arthur down in cold blood, and terrified, Kay begs for her life and offers herself to Sam. Asa, meanwhile, tries to sneak a gun out of his sack, but is interrupted by the wary, rifle-toting Dummy. On Dottie's suggestion, Larry then attempts to convince Bart, who is growing weak from his gunshot wound, to join their side. Despite Larry's insinuations that Sam will betray him for the money, Bart remains loyal to Sam. Soon after, Neal drives up, and Sam demands that he operate on Bart. While Dottie boils water in the kitchen and is propositioned by Sam, Neal and Kay discuss their failed marriage. Neal then prepares to anesthetize Bart with sodium pentothal, and Bart, suddenly nervous, asks for a Bible. Asa offers to get one from his sack and, while doing so, grabs his gun and slips it to Larry. Sam sees the exchange and viciously attacks Larry before he can fire the weapon. Fearing for Larry's life, Dottie, who has fallen in love with the reporter, screams at Sam to stop. Though he spares Larry, Sam slaps Dottie, then warns all the hostages not to try any more "heroics." Bart's surgery is a success, but Neal tells Sam that Bart will not survive if he is moved. Unknown to all of them, the Army has rescheduled the time of the blast, which is now due to occur in one hour. Later, as the unsuspecting fugitives prepare to depart, Kay tries unsuccessfully to reconcile with Neal, then pleads with Sam to take her with him. When Sam insists on tying up the hostages, a guilt-stricken Bart pulls a gun on him and demands their release. Just then, the five-minute warning alarm sounds, stunning everyone. Sam knocks the gun out of Bart's hand and hustles him to Neal's car along with Dummy and a hysterical Kay. Larry, Dottie, Neal and Asa flee on foot and race toward the hills. With only a minute to spare, Sam realizes that he is driving toward the bomb site and desperately turns around. Larry and the others, meanwhile, run into an old mine for protection. When the bomb finally explodes, Sam's car is swept up in the devastating blast. Larry, Dottie, Neal and Asa are untouched by the blast and, after the dust settles, emerge from the mine, finally free.
