A young woman marries against her father's will, but the happy life she expected turns into a series of tragedies.

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.

1939 film by Edmund Goulding