Enemy spies try to steal a new fighter plane.

Secret Service Major Steel (Joseph W. Girard), is one of the few men in America aware of the fact that Captain Albright (Dave O'Brien) is also Captain Midnight, daring masked aviator dedicated to fighting gangsters and enemies of America. When murderous bombing attacks are made on West Coast munitions plants, Steel sends for Albright and asks him to track down the mysterious Ivan Shark (James Craven), the foreign agent mastermind behind the attacks. Shark has learned about an ingenious range finder, invented by John Edwards (Bryant Washburn, and makes plans to obtain a model of the invention. Edwards instructs his daughter, Joyce (Dorothy Short), to bring the model to Albright for safekeeping in his mountain laboratory. Shark takes Edwards prisoner by Albright assures Joyce that her father will be saved and an end put to Shark's reign of terror. Dressing as Captain Midnight and enlisting the aid of his friends, Chuck (Sam Edwards) and Ichabod Mudd (Guy Wilkerson), Captain Midnight delivers on his promises fourteen chapters later.

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.

Texas Ranger tries to stop takeover of Indian lands.

The California-Yucatan Railroad, being built for the good of Mexico, is under siege by a gang of terrorists hoping to force its sale; no one can prove their connection to profiteer Marsden. Manuel Vega, aged co-owner, calls in the aid of his nephew James, great-grandson of the original Zorro. Alas, James seems more adept at golf than derring-do; but after he arrives, Zorro rides again! Can one black-clad man on horseback defeat a gang supplied with airplanes and machine guns?

Deadwood Dick, a masked and mysterious hero, is in reality Dick Stanley, editor of the Dakota Pioneer Press and a leading member of Statehood For Dakota. He is on the trail of a masked villain known as the Skull, who leads a violent, renegade band infamous for its violence against the Deadwood residents' wishes for a statehood status.

New York City policewoman Casey Jones' assignment to fight crime often entails her going undercover in some of the seediest and most dangerous parts of the city.

A crime fighter known as The Spider battles a villain called The Octopus, who is out to sabotage America and install his own government.

An adventurer goes after Nazi spies who have a new death ray called the Paratron.