This serial is most remembered for its first chapter that ends with John Wayne, on a deserted country road, running and dodging a bi-plane that is trying to run him down. Similar to Alfred Hitchcock's Der unsichtbare Dritte (1959).
CHAPTER TITLES: 1. The Carnival Mystery; 2. Pinholes; 3. The Eagle Strikes; 4. The Man of a Million Voices; 5. The Telephone Cipher; 6. Code of the Carnival; 7. Eagle or Vulture?; 8. On the Spot; 9. When Thieves Fall Out; 10. The Man Who Knew; 11. The Eagle's Wings; 12. The Shadow Unmasked.
Scenes showing the plane skywriting messages high in the air are actually stop-motion animation. Possibly done by Disney.
The maker of the dummy used in this movie was Theo Mack of Chicago, Illinois. The dummy has no name in the movie.
The scene of the plane in a spiral dive in Chapter 1 is repeated again in Chapter 11. This scene has been used in other Mascot movies, like, Hurricane Express (1932), Chapter 2.