A Martian invader crashes his spaceship conveniently close to the workshop of a scientist who is developing an interplanetary craft. If the extraterrestrial Purple Monster can complete the rocket ship and return to Mars, he will be able to start a full-scale invasion of Earth. Good thing Craig Foster sets out to thwart the Monster's mission!
Roy Barcroft
as The Purple Monster
Dennis Moore
as Craig Foster
Linda Stirling
as Sheila Layton
James Craven
as Dr. Cyrus Layton
Bud Geary
as Hodge Garrett
Mary Moore
as Marcia
John Davidson
as Emperor of Mars
Joe Whitehead
as Carl Stewart
Emmett Vogan
as Saunders
George M. Carleton
as Dr. Paul Meredith
Kenne Duncan
as Charles Mitchell
Rosemonde James
as Helen
