He finds a crashed Italian airplane surrounded by hyenas. Tarzan quickly disperses the beasts and finds the pilot dead in the cockpit, killed by a bullet through the throat. Footprints around the plane reveal that passengers have left the scene. Further investigations show that the pilot was shot from above, so Tarzan concludes that he was shot by someone in another plane. Tarzan smells a glove and gets another clue.
Footprints tell of two men who left two days ago.
Tarzan follows the two men and finds a second plane wreck, this one shot down by a machine gun. He is an Englishman, Lieutenant Cecil Giles-Burton. Tarzan decides to follow him. The Thread of Fate Horace Brown has invented a device designed to disrupt the ignition system of any internal combustion engine. Mary Graham tells the secret to Joseph Campbell, who along with Nikolai Zubanev, murders Brown and steals the plans.