THE HUMAN DUPLICATORS

Aboard a spacecraft heading toward Earth, the head of the "Intergalactic Council" briefs Dr. Kolos, a gigantic humanoid alien, on his part to "expand our galaxy domination program." If Kolos succeeds, human duplicates—androids—will begin taking over. If he fails, he will be destroyed.

After arriving via "teletransporter" at the mansion of Dr. Vaughan Dornheimer, Kolos encounters Dornheimer's blind niece Lisa. Not realizing that he is an extraterrestrial, she takes Kolos to Dornheimer's laboratory. Kolos tells Dornheimer that together they will develop the sophisticated androids that Dornheimer is unable to create on his own. Dornheimer refuses, but Kolos makes clear that he is now "the master" and that he will be obeyed.

The police, meanwhile, are stymied by multiple thefts from high-security electronics facilities, apparently perpetrated by the "top scientists" who are employed there. Most baffling of all is Dr. Munson. After being admitted to his facility, he tears a security door off its hinges with his bare hands and kills a security guard. He then ignores shouted warnings to halt by a second guard, who shoots him four times in the back. Munson does not react to his wounds while escaping in his car. He is an android, although the police do not know it.

Glenn Martin of the National Intelligence Agency (NIA) takes over the case. Glenn fails to uncover any clues by later posing as a reporter at the home of Dr. Dornheimer, although he does encounter Lisa. He later sneaks into Dornheimer's lab and witnesses human duplication. Lisa tells him that Dornheimer has been replaced by an android. As she leaves, Glenn is attacked by an android version of Dornheimer's servant Thor. In the ensuing fight, Glenn smashes android Thor's head, destroying him. Kolos apprehends Glenn so that he can be duplicated.

After duplication, android Glenn returns to NIA headquarters, where Gale Wilson, Glenn's girlfriend and fellow agent, notices his oddly cold behavior. Concerned for his well-being, she decides to surreptitiously follow him.

Android Glenn goes to a facility to steal additional electronics needed for duplication. He is interrupted by Gale, and soon engages in a gunfight with the police, during which his arm is trapped in a sliding door. When the police pry the door open, they mysteriously find android Glenn's arm left behind, which was apparently torn off while escaping.

Meanwhile, the real Glenn is locked in a cell with the real Dornheimer. Lisa brings Glenn his "lucky coin," which contains a length of wire that can be used to cut through the cell's bars. She is then dragged away by two android lab assistants. As he saws the bars, the real Dornheimer tells him that he can destroy the androids by zapping their heads with the lab's "pulse laser beam."

When Kolos refuses to turn Lisa into an android, android Dornheimer proclaims himself head of the android "master race" and has Kolos chained to a wall by the half-dozen android Thors it takes to overpower him, then begins the process of duplicating Lisa. However, android Glenn returns, interrupting the duplication. Still loyal to Kolos, android Glenn refuses to accept android Dornheimer as his master. They fight, destroying each other. The real Glenn uses the pulsed laser beam to destroy the remaining androids as Kolos breaks free of his chains.

After the Thor androids have been destroyed, Kolos gently places the unconscious Lisa on a sofa. Her eyelids flutter open. She touches a tear on her cheek and smiles.

Kolos later says that his mission has failed and, sadly, he has learned that he too is an android. He teletransports back aboard the spaceship, presumably to meet his doom at the hands of the Intergalactic Council.

After a series of confrontations, the real Glenn and Dornheimer, with Lisa's help, manage to destroy the androids using the laboratory's pulse laser beam.

The ending emphasizes the vulnerability of even the most meticulous invasion schemes when faced with human ingenuity and unexpected alliances. Lisa’s bravery and Glenn’s resourcefulness tip the scales, highlighting the film’s theme of individuality prevailing over mechanical conformity. The destruction of the androids resets the balance, leaving humanity temporarily safe—at least until the next flying saucer arrives.