The cruel captain of a schooner dominates the shipwreck victims he picks up.

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.

In order to save his family from financial ruin, an English aristocrat agrees to come to America and marry the daughter of a wealthy businessman. Once there he can't bring himself to do it.....

A playwright, Wakefield, Jr., turns detective when his father is killed after nearly capturing two brothers in possession of four rubies belonging to the British Museum. An investigation suggests that "the Breen girl" is responsible for Wakefield's death, and the younger Wakefield pursues her across the ocean to the United States.