This was another of Republic's titles to use a play-on-words for "King of..." "King" was actually the name of the main character.
As in other Republic serials, Republic's top stuntmen, Dale Van Sickel, Tom Steele and David Sharpe, not only did stunts for other actors, they were given multiple roles throughout the serial. The audience were meant to see only one episode per week and therefore not expected to remember the faces of each henchman or extra.
CHAPTER TITLES: 1. Dr. Vulcan. Traitor; 2. Plunging Death; 3. Dangerous Evidence; 4. High Peril; 5. Fatal Dive; 6. Mystery of The Rocket Man; 7. Molten Menace; 8. Suicide Flight; 9. Ten Seconds To Live; 10. The Deadly Fog; 11. Secret of Dr. Vulcan; 12. Wave of Disaster [NOTE: The On Screen number to this is 'Last Chapter' instead of '12'].
The exterior entrance to the Science Associates Administration is the same one as used for Commando Cody's office in Radar Men from the Moon (1952).