The Eagle uses sky writing to make threats against a corporation. Nathan Gregory owns a traveling fairground and is thought to be the Eagle. Craig McCoy is a pilot who goes looking for the Eagle when Gregory turns up missing.
Dr. Herbert Lee (John Paul Jones), an archaeologist seeking to decipher ancient Mara inscriptions, is aided by his son, Terry (William Tracy), and Terry's pal, Pat Ryan (Jeff York), and Normandie Drake (Joyce Bryant). Fang (Dick Curtis), a jungle pirate and warlord,plots to kill The Dragon Lady (Sheila Darcy), Queen of the Temple of Mara, and seize the treasures of her ancestors. Both Fang and The Dragon Lady have sworn death for any foreign intruders.
Professor Davidson and his niece Diana Palmer search Africa for the Lost City of Zoloz, reputed to be the source of a large hidden treasure. Also searching is a local crook, Singapore Smith, and Dr. Max Bremmer, who plans to destroy the peace in which the native tribes have been living. However, Godfrey Prescott, otherwise known as the Phantom, is feared and respected by the natives and is able to circumvent the traps and schemes of the villains.
Homesteaders are moving into the valley settled many years ago by rancher Craig Dolan. He wants to keep them out by legal means but his nephew Bart brings in outlaws to drive them out. The Lone Ranger is on hand to help the homesteaders battle Bart's men as he overcomes traps, ambushes, burning buildings and other obstacles in his attempt to bring peace to the valley.
A murderous gang of counterfeiters has kidnapped the government's best engraver and is forcing him to print virtually undetectable phony money. The Secret Service sends its toughest agent, Jack Holt, and a female partner after the gang.