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.
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 scientist invents a poison gas; the villain and his gang will do anything to get the formula; our hero, "Lightning Hutch", is sent to save the scientist, the scientist's beautiful daughter, and the formula.
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.

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