CHAPTER TITLES: 1. Beneath The Ocean Floor; 2. Undersea Kingdom; 3. Arena of Death; 4. Revenge of The Volkites; 5. Prisoners of Atlantis; 6. Juggernaut Strikes; 7. Submarine Strikes; 8. Into The Metal Tower; 9. Death In The Air; 10. Atlantis Destroyed; 11. Flaming Death; 12. Ascent To The Upperworld.
Shot in 25 days.
The Volkite robots here, refurbished, became the "Republic Robot" that debuted in Mysterious Doctor Satan (1940). They appear again in Zombies of the Stratosphere (1952).
When Republic Pictures learned that Universal was producing its "Flash Gordon" serial, it rushed this serial, using similar plot elements, into production.