A 14-episode serial in which Mala, a Polynesian in the employ of U.S. Intelligence investigates sabotage on Clipper Island. A gang of spies causes the eruption of a volcano, for which our hero is blamed. He convinces the local Princess Melani of his innocence and helps her ward off a takeover by rival high priest Porotu.
The struggle over the Bellamy estate ends with Michael Bellamy accused of murder and killed on the way to prison, while his brother, Abel Bellamy, takes control of the estate for his own nefarious plans.
Beyond Hell's Gate Pass is territory controlled by a man who calls himself King Carter; he uses a variety of schemes to prevent the railroad from being built, for fear it will finish his control of (what he considers) his land.
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?
Hank Davis, foreman on a huge dam project, enlists the aid of his two flyer friends when a sinister figure known as The Black Ace leads his Mystery Squadron of masked pilots in an attempt to destroy the dam.
Hammond, owner of the town's stagecoach line and a leading citizen, is opposed to Idaho becoming a state, and kills Randolph Meredith, owner of the town's newspaper, for endorsing it. Meredith's sister Barbara, expert with a bullwhip and pistol, dons a black costume and mask and becomes "The Black Whip", dealing a blow to Hammond and his gang each time they perform some heinous act in their efforts to keep the town, and their power over it, unchanged. Aided by government agent Vic Gordon, Barbara confronts Hammond in a final showdown just as the town votes on whether or not to accept statehood.