Directed by Ford Beebe, Ray Taylor | Starring: Buster Crabbe, Charles Middleton, John Hamilton, Carol Hughes

A mysterious plague, the Purple Death, ravages the earth. Dr. Zarkov, investigating in his spaceship, finds a ship from planet Mongo seeding the atmosphere with dust. Sure enough, Ming the Merciless is up to his old tricks. So it's back to Mongo for Flash, Dale, and Zarkov.