The Brain Eaters

A man carrying a lit glass container bumps into a pedestrian in Riverdale. The container shatters, and a fight erupts as onlookers watch. The event hints at a mysterious threat connected to the strange object later seen in the woods.

Glenn Cameron and Elaine, distracted by a strange light, follow it into the nearby woods. They find dead animals and a metal structure resembling a rocket nose cone buried nearby. This discovery marks the beginning of a larger, unfolding mystery.

Two days after the Riverdale incident, a Senate committee in Washington, D.C. reviews classified army footage of the object. They also learn about a string of murders in the town, linking the killings to the mysterious device. Sen. Walter Powers and his assistant Dan Walker fly to Riverdale to investigate.

Sen. Powers, Dan Walker, Glenn, and Alice Summers join the investigation at the object's location. Dr. Paul Kettering records test results as they assess the structure. They confirm the cone is indestructible and contains a maze-like interior tunnel system.

Mayor Cameron returns to his office acting oddly as if possessed. He struggles to aim a pistol at himself, creating chaos in the hallway. A deputy ultimately shoots and kills him, revealing the parasite's reach into Riverdale's leadership.

During the autopsy, doctors discover a dead creature attached to the mayor's neck that injected a toxin into his nervous system. They note he would have died within 24–48 hours even without being shot. The parasite's presence ties the mayor's fate to the broader invasion.

On the highway, a man lying in the road is attacked by another man with a glass container. The sheriff is knocked out, and the two attackers remove something from the container before driving off in the sheriff's car. The incident signals the parasite's spread beyond Riverdale.

Aided by Alice, Kettering experiments with a piece of the creature that infected the mayor. The parasite attaches itself to Kettering, and he frees himself by burning it. The test confirms the parasite's ability to invade hosts and resist ordinary methods.

Paul and Glenn encounter Prof. Helsingman, a dying member of a missing expedition who vanished five years earlier. He utters the word 'Carboniferous,' hinting at a geologic origin for the invasion. They take clues from his words as they push toward the cone.

Three groups search for additional metal objects and discover two glowing containers holding more parasites. Senator Powers attempts to warn the governor via the telegraph, but the telegrapher is possessed and fails to send the message. The danger continues to mount as the warning is not delivered.

Three men plant a parasite in Alice Summers' apartment, and she is taken over by the invaders. Realizing she has been compromised, Paul and Glenn race back toward the cone to intervene and thwart the spread.

Kettering and Glenn reach the cone's inner chamber and meet an expedition member who reveals the parasites' deeper motive. The plan to overthrow conflict comes with a deadly price as Alice, now possessed, kills Kettering. Glenn fires a harpoon to bridge to a high-voltage line, electrocuting the parasites as the cone is destroyed. Alice collapses, and Glenn and Elaine walk away embracing.