A television announcer reports sightings of a red fireball around the world. Facetiously, he calculates its path will lead it to California. Nancy Archer (Allison Hayes), a wealthy but highly troubled woman with a history of emotional instability and immoderate drinking, is driving on a road in an American desert that night. A glowing sphere settles on the deserted highway in front of her, causing her to veer off the road. When she gets out to investigate, a huge creature exits the object and reaches for her (the viewer sees only an enormous hand falling upon the screaming woman). Nancy escapes and runs back to town, but nobody believes her story due to her known drinking problem and recent stay in a sanatorium. Her philandering husband, Harry Archer (William Hudson), is more interested in his latest girlfriend, town floozy Honey Parker (Yvette Vickers), but pretends to be the good husband in the hope that Nancy will "snap" and return to the "booby hatch", leaving him in control of her $50 million.
Nancy bargains with Harry, asking him to search the desert with her for the "flying satellite," agreeing to a voluntary return to the sanatorium if they find no evidence. As night falls, they find the spacecraft. The alien creature, now seen as an enormous male humanoid, emerges. Harry fires his pistol at it, but the gunfire has no effect on the creature. Harry flees, leaving Nancy behind.
Nancy is later discovered on the roof of her pool house, but is delirious and must be sedated by her family physician, Dr. Cushing (Roy Gordon). The doctor comments on some scratches he finds on Nancy's neck, and theorizes that she was exposed to radiation. Harry, egged on by his mistress Honey, plans to inject Nancy with a lethal dose of her sedative, but when he sneaks up to her room, he discovers that she has grown into a giant. (In a scene paralleling that of Nancy's first encounter with the alien, the viewer sees only an enormous prop hand as the film characters react in horror.) Cushing and Dr. Von Loeb, a specialist he has called in, are at a loss how to treat their patient. They keep her in a coma with morphine and restrain her with chains while waiting for the authorities. The sheriff and Jess (Ken Terrell), Nancy's faithful butler, track enormous footprints leading away from the estate to the alien sphere. Inside the sphere, they find Nancy's diamond necklace (containing the largest diamond in the world) and other large diamonds, each in a clear orb. They speculate that the jewels are being used as a power source for the alien ship. The huge alien reappears, and the sheriff and Jess flee.
Meanwhile, the gigantic Nancy awakens and breaks free of her restraints. She tears off the roof of her mansion and, clothed in a bikini-like arrangement of bed linens, makes her way to town, to avenge herself on her unfaithful husband. When she rips the roof off the bar to get at Harry, she spots Honey. She drops a ceiling beam on her rival, killing her. Harry panics, grabs Deputy Charlie's gun, and begins shooting, but she picks Harry up and walks away. Gunshots have no apparent effect on her. The sheriff fires a riot gun, which causes a nearby power line transformer to blow up, killing Nancy. The doctors find Harry lying dead in her hand.
Where do Harry and Nancy find the spacecraft?
The desert