Roy Barcroft, Dennis Moore, Linda Stirling, James Craven, Bud Geary, Mary Moore, John Davidson, Joe Whitehead, Emmett Vogan, George M. Carleton, Kenne Duncan, Rosemonde James, Monte Hale
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!