Title and credits run over a desert vista and a car driving on a dirt road. We open in the broadcast studio of KRKR-TV and the newsman (an uncredited Dale Tate) reporting on the worldwide sightings of a UFO. Referring to a globe, he traces the cities reporting and concludes, "The stranger from space should be over our California desert in a matter of minutes." A 1958 Chrysler Imperial races down US Route 66. A large spherical object comes into frame and sets down on the highway causing the car to first swerve, then stop. Behind the wheel is a very drunk and distraught Nancy Fowler Archer (Allison Hayes). She screams while trying to start her car. She gets out and is menaced by a huge hand while screaming, "No! No!" She is clutching a large diamond pendant around her neck. She escapes and runs down the road. In Tony's Bar and Grill, we meet Nancy's philandering husband, Harry (William Hudson) and his latest gold digging girlfriend, the aptly named, Honey Parker (Yvette Vickers). Harry and Honey are getting intimate. Harry tells Honey that returning to his wife after their separation was a mistake, but he needed the cash, and Nancy is loaded. She is worth about $50 million. "A man hasn't got a chance," Harry concludes regarding community property. "Unless the wife dies," Honey reminds him. Harry registers visible shock, so Honey backs off. Another thought comes to mind--recommit Nancy to the nut house. At that Nancy runs into the parking lot and is intercepted by Deputy Charlie (Frank Chase). The commotion stirs Sheriff Dubbitt (George Douglas). The sheriff clears the crowd and mindful of Nancy's money and influence handles the situation with kid gloves. He sends his deputy to find Harry. When Dubbitt suggests black coffee, Nancy reacts with rage and anger, "Black Coffee? You think I'm drunk, don't you?" She pleads, "You've got to believe me. It was right in the middle of the highway, thirty feet tall. It lit up the sky. You don't believe me, do you?"
Charlie finds Harry and Honey in a booth necking. He reluctantly interrupts the couple. He accepts a monetary gratuity from Harry who adds, "You couldn't find me tonight, Charlie. I took a cab home." The sheriff directs Charlie to, "Go get the riot gun. We're taking a ride in the desert with Mrs. Archer." The three drive off in pursuit of Mrs. Archer's giant and satellite. All they find is Mrs. Archer's car. They make a cursory search to humor Mrs. Archer, but of course find nothing. Angry and frustrated, Nancy gets in her car and drives off. At the Archer estate, Nancy drives up and enters the house. She is greeted by her butler, Jess Stout (Ken Terrell). Nancy immediately heads for the bar to make herself a drink. Harry is laying on the couch and suggests to Jess to, "Beat it out of here." Jess only responds to orders from his boss, Nancy. Nancy tells her unfaithful husband he can go too, but he reminds her of her embarrassing episode with the police. They fight over his philandering and her alcoholism, but ultimately Nancy loves her husband and wants their marriage to work. She tells him of her roadside encounter with the satellite. She pleads with Harry to believe her story. He puts her to bed, gives her a sedative, snags her diamond pendant, then heads back to Tony's to see Honey Parker.
Back at Tony's, Deputy Charlie and Honey are dancing. Tony (Michael Ross) is serving drinks at the bar. Charlie excuses himself when Harry arrives. He is annoyed that Honey wasn't at the hotel. Honey is even more annoyed by that, "Fleabag you call a hotel and I'm tired of waiting." Harry tells Honey his wife is cracking up and shows her the diamond, the Star of India, as an inducement to bide her time and stay the course.
Dr. Isaac Cushing (Roy Gordon) makes a house call on his richest patient. "She's not well, Harry," is the doctor's conclusion. Cushing adds, "She's suffering from mental exhaustion, and her drinking doesn't help her any." The doctor leaves as Nancy walks down the stairs from her room. They resume their fight about his activities, thanks to updates from Jess, and her delusion about a giant and a satellite. Harry returns her diamond pendant then walks upstairs. While Nancy drowns her sorrows in the bottle, the KRKR-TV reporter rubs salt in the wound with a news item about Nancy. Her story is now fodder for the public along with a strong inference her alcoholic hallucinations are responsible for the fantastic tale. A well-aimed bottle thrown at the TV stops the report, but not the hurt and humiliation. Jess and Harry run into the room. Nancy orders Jess to get the car and Harry to accompany her into the desert to find it. Before they leave she orders Jess to get a revolver.
Harry drives while Nancy looks for her satellite. They drive for hours and find nothing, "Just sand and space." That evening Nancy spots a flash of light. She is convinced it is her satellite, but they still find nothing. Nancy breaks down and apologizes. As they drive off she spots it. She runs up to it. She presses her hands against it, explaining, "It's real. It's real. I'm not crazy. I did see it." Harry pulls his wife away as a Giant (Michael Ross, again) reaches out to her. Harry fires the revolver point blank at the creature. As Nancy screams, "Harry, help me!" Harry for his part drives off leaving his wife to the giant. Harry arrives at the house, runs past Jess and begins packing his suitcase. Jess demands, "What have you done with Mrs. Archer?" Harry ignores him and continues to pack. They scuffle on the stairs and continue their fight in the living room. An empty liquor bottle across his head stops Jess. Harry grabs his suitcase and leaves the house. Jess comes to and calls the sheriff's office. Harry arrives at Honey's hotel room and tells her, "Get dressed and packed, quick." Before they can leave her room they are stopped by Deputy Charlie and the night clerk. This time Charlie refuses the customary bribe and takes the pair to see the sheriff.
Charlie, Harry and Honey wait at the sheriffs office. The sheriff and a posse were out looking for Mrs. Archer. A phone call informs the three that Mrs. Archer was found on the pool house at the Archer estate. The three drive back to the house. At the house, Cushing and the nurse (Eileen Stevens) finish attending to Nancy and come down the stairs. Dr. Cushing tells Dubbitt she should be moved to a hospital when she's strong enough. Cushing is most concerned about the scratches on her throat. Harry tries to sprint upstairs, but Dr. Cushing warns him that she may be contaminated by radiation. The sheriff asks Harry where he was with Mrs. Archer the night before. Harry lies and tells him he was with Honey all evening. Honey corroborates the lie. The sheriff warns Harry and Honey not to leave town. In the car heading back to town, Honey again suggests a bit of murder to solve their problem. She informs Harry, "I heard the doctor tell her (the nurse) that an overdose would be fatal." Harry sarcastically replies, "Money certainly brings out the best in you, doesn't it?" Honey presses, "Have you got the nerve?" Harry has taken the bait. As the nurse sleeps, Harry fills the syringe and creeps upstairs to their bedroom. As he approaches his sleeping wife in the dark, the nurse catches him red handed when she turns on the light. The nurse screams and calls for the doctor as Harry recoils from the giant hand and arm. "Doctor Cushing, something's happened to Mrs. Archer," the nurse screams again.
The next day a delivery is made. Meat hooks, lengths of chain and medical supplies are delivered to the Archer residence. Dr. Cushing consults with Dr. Heinrich Von Loeb (Otto Waldis) but Von Loeb is stumped by the cause of the giantism and the blue-green color around the scratches at her throat. He suspects radiation.
At the hotel, Honey amuses herself with her record player. She was expecting Nancy to be dead, and tells Harry so. Harry reports she's still in a coma. The sheriff and deputy search the pool house area. Dubbitt notices a giant footprint in the garden below. Charlie spots a couple more prints. Dubbitt sends Charlie back to the office for weapons. He and Jess follow the footprints in Archer's station wagon out into the desert. They spot the satellite and walk up to explore it. Dubbitt concludes the giant brought Mrs. Archer home and placed her on the pool house roof. Jess finds his gun confirming the Archer couple's presence. Dubbitt and Jess cautiously enter the open satellite and walk past walls made of pegboard and past discharging fire extinguishers. They find a series of glass spheres containing various colored gemstones. They find Mrs. Archer's Star of India diamond. They encounter the giant and retreat out of the space craft. Unable to move the car, they abandon it just before the giant, dressed in a leather Viking tunic, overturns it. The giant is impervious to bullets and grenades. The giant reenters his satellite and departs. Dubbitt and Jess walk back to town.
At the Archer house, Cushing and Von Loeb discuss Nancy's case and their own lives. Nancy wakes from her coma and calls for her husband. Harry and Honey are dancing at Tony's Bar and Grill. Charlie informs Harry that there is an emergency at home. Harry is indifferent to the situation and sends Charlie on his way. Back at the house, the sedative is not working. Nancy is awake again and calling for Harry. They try to administer more morphine, but Nancy breaks free. She tears the roof off her room and escapes. The house begins to come apart and Cushing, the nurse, and Von Loeb barely escape. Nancy is single minded now, "I know where my husband is. He's with that woman. I'll find him." Nancy strolls casually to town wearing a makeshift bra and skirt made from bed sheets.
On his way to the Archer house, Charlie encounters Dubbit and Jess on the road. He stops and picks them up and continues to the Archer home. They pick up Cushing, Von Loeb and the nurse. The six drive back to town. Out in the desert, an old prospector (an uncredited Thomas E. Jackson) spots Mrs. Archer heading for town. Nancy stops and shakes an electrical transmission tower knocking out the power at Tony's place. She then casually strolls up to Tony's, scares a young couple in their car, then heads for the hotel. She tears the sign off the hotel screaming, "Harry!" Nancy breaks a window and pushes her giant hand into Honey's bedroom leaving it a shambles. She strolls back to Tony's and calls for her husband. Harry takes Charlie's gun and shoots his wife's giant hand as it comes through the door. Nancy tears the roof off the building. Spotting her quarry Honey Parker, Nancy throws the roof beams and rafters down on the table Honey is hiding under. Honey is dead, and Nancy now directs her wrath at Harry. She picks him up and carries him through the open roof. He complains, "You're crushing me. I can't breathe." Dubbitt fires a few shots at Nancy Archer but they have no effect. He finally places a carefully aimed shot at a transformer which explodes, electrocuting Nancy and Harry Archer. Both dead on the ground, Nancy is still clutching Harry in her hand. The doctor ironically remarks, "She finally got Harry all to herself." We close with a long-shot of the doctors and townsfolk surrounding the dead bodies of Nancy and Harry Archer.