A murderous gang of counterfeiters has kidnapped the government's best engraver and is forcing him to print virtually undetectable phony money. The Secret Service sends its toughest agent, Jack Holt, and a female partner after the gang.
Captain Dan Tempest was an ex-pirate who received a pardon from the King and turned privateer after his stronghold of New Providence was taken over by Crown soldiers. Tempest and Lt. Beamish, the Crown-appointed deputy governor, were uneasy allies, fighting the Spanish privateers who were ravaging the Caribbean.
The period is the 1820's and the first wagon train leaves Independence heading west to Santa Fe. In order to maintain his power, the ruthless Official at Santa Fe must not let them arrive and he sends out his men to stop them. The wagon train then has to endure repeated attacks but is aided by a mysterious rider that shoots singing arrows and rides a painted stallion.
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.
Homesteaders are moving into the valley settled many years ago by rancher Craig Dolan. He wants to keep them out by legal means but his nephew Bart brings in outlaws to drive them out. The Lone Ranger is on hand to help the homesteaders battle Bart's men as he overcomes traps, ambushes, burning buildings and other obstacles in his attempt to bring peace to the valley.
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.