A heavy condensation of the 1936 serial Flash Gordon, with altered musical score. Flash Gordon, Dale Arden and Dr. Hans Zarkov visit the planet Mongo to thwart the evil schemes of Emperor Ming the Merciless, who has set his planet on a collision course with Earth. Released abroad as "Flash Gordon" for countries not interested in booking the serial, and never shown in the USA before 1950, where the title was changed to "Rocket Ship".

Flora Hawks is in love with the overseer of Tarzan's African estate. After a search for a legendary city of diamonds, Tarzon races with his pet lion Jad-bal-ja to save Haws from being sacrificed to a lion-god.