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.

Larry Munro has discovered a vein of platinum on his ranch. A group known as the Secret Seven has learned about it and plan to get the Munro Ranch. Kentucky Wade and his friends arrive to help Larry and are soon fighting off attempts on their lives by the henchman of the Secret Seven and the Indians they enlist by bribing them with rifles.

An expedition arrives on an uncharted jungle island to rescue the local natives, led by a jungle boy, from a volcano that is about to erupt.