Two mysterious white circles glide across a solid black screen, accompanied by a calm female voice explaining their mission: to inhabit human bodies in order to carry out their plan.
On a quiet beach near Cape Canaveral, a man and a woman head toward the future, unaware that the circles are watching. The circles descend, and the car they’re in crashes. Both people die—or so it seems—until the body’s consciousness is taken over by the alien visitors. The male alien, Hauron, and the female alien, Nadja, reanimate the pair, turning a tragedy into a strange, new life. Nadja retrieves Hauron’s severed arm, which she promises to reattach at their hidden laboratory—an artificial cave that serves as their headquarters and breeding ground for their experiments.
When Hauron scouts Cape Canaveral at night, a guard dog attack tears off the reattached arm. Undeterred, he wields a disruptive ray to sabotage rockets as they launch, while the human scientists below scramble to understand why their missiles explode. The threat is hidden in plain sight, and the launch site hums with the quiet tension of a force they cannot name.
At the same time, Tom Wright and Sally Markham, colleagues at the launch facility, enjoy a simple evening out with friends, Bob Harding and Shirley. Tom notices static on a transistor radio—evidence, he suspects, of an illegal transmitter nearby that could be connected to the launch failures. The foursome decides to investigate, hoping to uncover a human culprit behind the sabotage.
Their search takes a dark turn when Bob Harding and Shirley are kidnapped by the alien pair. Bob dies during the capture, and Nadja removes his arm to graft onto [Hauron], even offering to replace Hauron’s scar with Bob’s chin, arguing that it gives the alien a more handsome look. Shirley and Bob are sent to the aliens’ planet, a troubling sign that the invaders may be collecting specimens, dead or alive, despite prior warnings.
Unaware of Bob’s fate, Tom and Sally press on and stumble into the cave themselves, where they are kept in place by an electromagnetic device. Tom discovers a weakness and frees himself by waving a wristwatch with a radium dial at the field. He escapes to seek help, but he cannot leave Sally behind and returns to her side.
Relief arrives in force—sheriff’s deputies, Army personnel, and rocket scientists rush to challenge the intruders. The captives demand the aliens surrender, yet Nadja and Hauron prove to be elusive, slipping back into their circular form to transmit themselves home. The rescue party recovers just in time, and Tom, along with the head rocket scientist for Sally, devises a plan to stop the extraterrestrials from transmitting themselves again. The cave erupts in a powerful explosion, and the team breathes a cautious sigh of relief as the space program appears to be safe.
Yet the story lingers on a fragile note. As Sally Markham climbs into a patrol car with a deputy—an ordinary drive that suddenly fills with tension—the tires screech, a crash echoing through the air, and Sally’s scream reminds us that the threat may not be fully over.
