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.

• Universal Pictures
• King Features Syndicate
• Buster Crabbe
• Carol Hughes
• Charles Middleton
• Anne Gwynne
• Frank Shannon
• John Hamilton
• Herbert Rawlinson
• Tom Chatterton