Dr. John Meredith has been driven from civilization by the criminal activities of his twin brother Bradley Meredith. With his infant daughter, he settles in the African jungle, where his ability to cure the native ills has resulted in his virtual control of the Masamba tribes, who possess vast diamond mines coveted by a gang of crooks. They use Shamba, a witch doctor jealous of Dr. Meredith's influence over the tribe, to further their schemes. They lure Dr. Meredith away from the jungle, and he is murdered by "Slick" Latimer. The natives believe that a sacred amulet is the secret of Dr. Meredith's power, and Shamba attempts to kill Nyoka, Meredith's now-grown-up daughter, to obtain the amulet (which actually contains the secret to the entrance of the Caves of Nakros). Jack Stanton rescues her and assists her in her efforts to recover the amulet. Latimer works with Shamba, and with Bradley Meredith, who poses as his murdered-brother so successfully that even Nyoka does not realize the deception.

American, British and Chinese secret agents battle the Japanese Black Dragon Society, a secretive ring that smuggles enemy agents into the U.S. disguised as mummies.

Foster (Charles Miller (IV)', owner of the local stagecoach line in Canyon City in the 1880s, has received a Federal Franchise Commission grant and is rushing to complete a new road through the lawless Comanche Strip with the aid of his daughter, June (Kay Aldridge), and his construction foreman "Red" Kelly (Eddie Acuff). Unbeknownst to them, their supposed friend, land-and-cattle dealer Martin Dexter (Robert Frazer), and the town lawyer, Silas Higby (Ted Adams), have plans of their own; should Foster's road see completion, homesteaders would occupy the strip and ruin Dexter's plans to buy the 500,000 acres for cattle-grazing land. Dester hires a band of renegade Indians to attack the road crew. Indian scout Jim Brady (Budd Buster)sees a supply wagon driver by "Red" and June being cased by the renegades, alerts the work-camp crew and then rides to summon Captain Duke Cameron (Allan Lane) and his U.S. Cavalry troop but, before they arrive, Foster has been killed along with many of his workmen. Cameron, a long-time friend of the Foster family, later requests his commanding officer, Colonel Andrews (Stanley Andrews) for a furlough to aid June in continuing her father's project. He then seeks to find out who is behind the renegade attack and, eleven cliffhangers later does so in the final chapter of this 12-chapter serial.