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.

Pulp hero "The Spider" seeks to destroy all criminals. In this serialized adventure, he battles The Octopus, who intends to replace the government of the United States.