From his observatory, Scottish professor Elliot (Raymond Bond) keeps close watch on Planet X, whose orbit is coming close to Earth. During the planet's approach, an alien ambassador appears but falls prey to maniacal scientist Dr Mears (William Schallert). Returning the distinct lack of hospitality, the extraterrestrial uses his otherworldly powers to turn those he encounters into mindless drones. Elliot tries to stop the creature before everyone is turned into a zombie.