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.

The chapter-crunched version of this 196 minutes, 12-episode serial from Republic finds Canada being bombed mercilessly by a mysterious-enemy plane (shaped like a boomerang) called the Falcon, under the supervision of Admiral Yamata, Count Baroni and Marshal von Horst, chiefs of the Axis Fifth Column in Canada. No one can identify the plane until American inventor, Professor Marshall Brent, and his daughter Carol arrive with a new type of airplane detector. This poses a threat to the Axis chiefs in preparing western Canada for an invasion and they have him kidnapped by local Quisling Gil Harper. RCMP Sergeant Tom King attempts to rescue Brent, but the inventor is killed when a plane in which he is held captive crashes into a riverboat. Carol, determined to carry on her father's work and with King's aid, manages to prevent the enemy agents from capturing the detector, and destroys the device (many chapters later) when the agents make a last desperate attack on the cabin where it is hidden. She is captured and taken to the crater of a volcano, where the ring makes its headquarters.

Reporter Brenda Starr (Joan Woodbury) and her photographer Chuck Allen (Syd Saylor) get involved in a search for the loot from a payroll robbery. Cliffhanging action and adventure and a fair amount of comic relief follow them at every turn.

Crime lord Jim Belmont escapes FBI custody and begins a reign of thievery that is thwarted at every turn by Jerry Blake, the FBI's Operator 99.

Girl looking for father who disappeared years before in a jungle, finds herself battling greedy civilized people and savages alike.

A 20th Century pilot named Buck Rogers and his young friend Buddy Wade awake from 500 years in suspended animation to find that the world has been taken over by the outlaw army of Killer Kane.

Three government aviators called the "Flying G-Men", one of whom is disguised as "The Black Falcon", fight to protect the US and its allies from an enemy spy ring and to avenge the death of the fourth Flying G-Man.

A famous detective sets out to discover who stole $2 million in bonds.

A young radio cop and a beautiful girl try to stop an international criminal gang from getting their hands on the formula for a new bulletproof steel.

Ken Williams is determined to discover the identity of the mysterious Rattler, who preys upon railroads and transportation companies like that owned by Jane Corwin. The Rattler is especially difficult to catch because of his skill at disguising himself as other people.