A young girl journeys to Africa to find her father, an explorer who vanished in the jungle.

Prof. Millard pretends to be dead and helps Jeff King ferret out Vulcan, the evil traitor at the science academy. Donning his Rocket Man costume King goes from one hair raising rescue to the next in order to keep the newly invented Decimator out of the clutches of Vulcan and his minions.

Nat Cutler, known as Hawkeye, is a fur trader. With his faithful Indian companion Chingachgook, the last of the Mohican tribe, he fights to protect settlers against the raiding Huron Indians.

During the latter stages of the Civil War, a gang of supposed Confederates, headed by Alex Morel (Lionel Atwill), raid all gold shipments destined for Washington from Oro Grande, California. In the first chapter, "Murder By Accident", Captain Steve Clark (Dennis Moore), is recognized as a Union Secret Service agent by Morel's accomplice Trina Dessard (Virginia Christine), and, with his friend Idaho Jones (Joe Sawyer), is ambushed in the baggage car and sent to almost certain death when the car is un-coupled and plunges down the mountainside. Leaping to safety, in order to be around for the next 12 chapters, Idaho and Steve report to Colonel Sewell (Addison Richards) in Oro Grande, and Idaho introduces himself as a Wells Fargo detective to Cathy Haines (Wanda McKay), the Oro Grande company agent. Steve and Idaho learn that the Morel raiders are only posing as Confederates, and their headquarters are at Morel's "Golden Eagle" saloon. In a raid on the hideout, Steve's brother Jim (Gene Garrick) is killed by the gang. The next victim is Confederate Army Captain Clay Randolph (Regis Toomey) who has discovered that Morel is connected with a group of Prussian spies and gives Steve a clue before he dies. The clue leads Steve to a San Francisco dive owned by Abel Rackerby (Charles Wagenheim), who, thinking he has Steve in his power, exposes the ring's activities and operation methods. Aided by the San Francisco Secret Service, Steve escapes and returns to Oro Grande, where in Chapter 13, "Golden Vengeance", he and Idaho round up the spies.

An expedition sets off for the last land of Mu, where legend has it that a killer death ray is emitted from the eye of a golden idol.