CHAPTER TITLES: 1. The Voice From the Void; 2. The Queen of the Night Riders; 3. The Invisible Enemy; 4. The Fatal Message; 5. The Trackless Trail; 6. The Radio Riddle; 7. The Crimsom Clue; 8. The Doorway of Disaster; 9. When Time Stood Still; 10.Riding the Whirlwind; 11.The Capsule of Oblivion; 12.The Hoofs of Horror.
Low-budget producer Nat Levine scored a windfall by being able to cast Harry Carey and Edwina Booth, who just came off starring in the major MGM hit Trader Horn (1931). Booth was still recovering from a serious bout with a tropical disease contracted in Africa while on location for that film.