Considered one of the goriest horror films to come out of the 1950s, Arthur Crabtree's sci-fi/horror film now has cult status. A long-range radar installation and its surrounding Canadian wilderness becomes the host to something deadly. At first, when military personnel and civilians are struck down, the leaders suspect murder. But the autopsies reveal that each victim has had its spinal fluids sucked dry through a hole in the skull. Eventually the finger of guilt points to Professor Walgate, who has been experimenting with human thoughts, the results of which are invisible brain monsters. When a massive dose of radiation reveals the monsters, a gory showdown ensues.