This adventure novel is the ninth in the series and picks up where the action left off in 'Tarzan the Terrible'. Tarzan, Jane and their son Korak find an orphaned lion club, which Tarzan decides to take home and train. However when news gets out of Tarzan's discovery of the treasure chamber in the lost city, plots are concocted to try and steal his fortune. After he is captured and held captive by thieves, the race is on for him to try and save the gold and the diamonds.