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.

A mad doctor named Zanoff uses a drug to bring himself back from the dead after his execution in prison. Dick Tracy sets out to capture Zanoff before he can put his criminal gang back together again.

When sponsor Nottingham cancels King Russell's radio program, The Hot Shots try to change his mind. They not only fail but Nottingham's son forces them to take him back to Russell's ranch. Once there he starts playing practical jokes. With everyone disliking him and learning his father is coming, he has a plan to redeem himself.

The ramshackle Smoky River Ranch is all that stands in the way of a developer and a big real-estate deal, but the old man who owns the ranch won't sell it, because he has to take care of some down-and-out theater people to honor his dead son's memory. Frustrated, the developer sends in a pretty young girl to try to trick the old man into selling the ranch.