|Robert Clarke||John Lawrence|
|Margaret Field||Enid Elliot|
|Raymond Bond||Professor Elliot|
|William Schallert||Dr. Mears|
|Gilbert Fallman||Dr. Robert Blane|
|David Ormont||Inspector Porter|
From his observatory, Scottish professor Elliot 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 . 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.