Dr. Douglas Martin (Peter Graves), a nuclear scientist, crash-lands on a reconnaissance mission after a nuclear test and miraculously appears unhurt at the base later, claiming to have been captured by aliens who plan to conquer Earth with giant monsters and insects. The FBI investigates his story, but he is eventually cleared and decides to use existing technology to destroy the alien threat using calculations made with a slide rule. Martin escapes from the hospital, goes to the nearby electrical power plant, and forces the power control room supervisor to turn off the power for 10 seconds, destroying the alien base in a massive explosion that saves the Earth.