IT CONQUERED THE WORLD

Dr. Tom Anderson, an embittered scientist, has made contact with a Venusian creature, while using his radio transmitter. The alien's secret plan is to take complete control of the Earth by enslaving humanity using mind control devices; the alien claims that it merely desires to bring peace to the world by eliminating all emotions. Anderson agrees to help the creature and even intends to allow it to assimilate his wife Claire and friend Dr. Paul Nelson. The Venusian disrupts all electric power on Earth, including motor vehicles, leaving Dr. Nelson to resort to riding a bicycle.

After avoiding a flying bat-like creature which carries the mind control device, Dr. Nelson returns home to find his wife, Joan, newly assimilated. She attempts to force his own assimilation using another bat-creature in her possession, and he is forced to kill her in self-defense. By then, the only people who are still free from the Venusian's influence are Nelson, Anderson, Anderson's wife Claire and a group of army soldiers stationed in the nearby woods.

Nelson finally persuades the paranoid Anderson that he has made a horrible mistake in blindly trusting the Venusian's motives, allying himself with a creature bent on world domination. When they discover that Tom's wife Claire has taken a rifle to the alien's cave in order to kill it, they hurriedly follow her, but the creature kills her before they can rescue her. Seeing the loss of everything he holds dear, Dr. Anderson viciously attacks the Venusian by holding a blowtorch to the creature's face; Anderson dies at the alien's hand as it expires. Arriving on the scene too late to save his friend, Nelson sadly reflects on how Anderson's misguided ideals led to death and devastation, and muses that a solution to humanity's problems must ultimately be achieved by humanity itself.

Dr. Anderson realizes the Venusian's true intentions and attacks it with a blowtorch, dying in the process as the creature is destroyed. Dr. Nelson survives to reflect on the devastating consequences of Anderson's misguided alliance.

The ending underscores the dangers of seeking easy solutions to humanity's problems through external, authoritarian means. Anderson's tragic fate and Nelson's final reflection deliver a cautionary message: genuine progress must come from within humanity, not from surrendering autonomy to outside forces, no matter how alluring their promises.