Amateur astronomer John Putnam has recently moved to Sand Rock, Arizona, and attracted the affections of schoolteacher Ellen Fields. One night, their kiss is interrupted when a giant glowing mass in the sky crashes into an abandoned mine shaft in the nearby desert. John and Ellen visit the huge crater created by the crash's impact, and when John climbs in, he finds a glittery trail that leads to a spaceship. In the open door stands an alien, but John gets only a glimpse of its one glowing eye before it creates an avalanche that buries the ship. By the time John narrowly escapes, a newspaperman and Sheriff Matt Warren have arrived, and when he reports what he has seen, the men scoff that he must have suffered a blow to the head in the avalanche. Pete brings Ellen home, explaining that though the townspeople may deride him, he must pursue his discovery, and she agrees to help him. Although they momentarily glimpse an image in front of their car, they do not realize that the alien is watching them. The next day at the site, John encounters more opposition, not only from a phalanx of reporters, but from his old friend, scientist Dr. Snell. Later, a jealous Matt warns John that he will not allow Ellen to be harmed by John's "foolishness." Driving home, John and Ellen come upon their friends, phone engineers Frank Daylon and George. Frank, who hears an eerie whistle over the phone lines, asks John and Ellen to check one area of the lines while he and George check another. Finding nothing, John and Ellen return to report to Frank and George and discover their truck abandoned on the road, a blood stain on the door. John follows glittery tracks into the desert, where a glassy-eyed, robotic George emerges and assures them that nothing is wrong. John, spying Frank's body on the ground behind a rock, grabs Ellen and races back to town to enlist Matt's help. As soon as they leave, the real Frank and George awaken from being knocked out and see before them their robotic replicas, who explain that they are aliens and have taken on the men's appearances. The aliens reassure Frank and George that they are peaceful and will merely detain the men at their ship until the aliens are ready to leave Earth. Meanwhile, Matt does not believe John's story, and although he finally accompanies them back to the desert, he leaves in disgust when they find no trace of Frank and George. All three return to town, where Matt watches as John spots the alien Frank and George and chases them down the street. Hidden in a dark alleyway, the aliens, who sense that John understands them, inform him that if they are left alone to repair their ship, they will remain peaceful. That night, while John frets over whether he is doing the right thing by not attacking the aliens, he is called to Matt's office. The sheriff, concerned about that day's disappearance of people, including Dr. Snell, and electrical equipment, begins to believe John, and the two men visit the mine together. At the same time, the alien George abducts Ellen and brings her to the mine, where Matt reluctantly agrees to wait in the car while John explores outside. Within minutes, an alien uses Ellen's form to lure John into the mine. There, an obscured alien instructs John that its race is an advanced one and will continue to be pacifistic as long as no humans disturb them for the two hours they need to finish their repairs. The alien further explains that, although they desire contact with earthlings, humans are not yet developed enough to accept the aliens' frightening appearance. John refuses to agree until the alien shows itself, but then turns away in horror from the huge, one-eyed, bulbous creature. John reveals to Matt what he has learned, and the two return to town, where John finds that the aliens have visited his house. When he informs Matt, the nervous sheriff rounds up the local men to attack. Alone, John runs to the mine to warn the aliens, but when he arrives, the head alien, who now looks just like John, hears the townspeople approaching. No longer trusting John, it mournfully announces that they now must use their deadly laser weapon. John proposes that if the aliens release the earthlings as a show of faith, the men outside will cease attacking. Reluctantly, the aliens agree, and the unharmed humans crawl through the mine shaft to the crowd outside. After Frank and John set off dynamite at the mouth of the mine to block the entrance, the townspeople stand together to watch as the spaceship flies out of the crater in a burst of light. When Matt asks if they are gone for good, John explains that they will return when humans are ready to accept them.