Flying students Danny Collins (Johnny Downs), Jinx Roberts (Bobby Jordan), Scrapper Mackay (Ward Wood) and Zombie Parker (Billy Benedict) are suspected of a series of murders perpetrated by a Nazi agent known as the Black Hangman. The latter is an engineer, Arthur Galt (Robert Armstrong), who has disposed of several people who accompanied him on an expedition which located lost helium deposits in Africa. Galt has also imprisoned the remaining members of the expedition, Professor Mason (Selmer Jackson) and his daughter Andre (Jennifer Holt). Galt plans to sell the helium to Germany through a Gestapo ring headed by Karl Von Heiger (Eduardo Ciannelli). The four cadets, thinking Galt is their friend, fly with him to Africa as they hope to track down Von Heiger, thinking he is the Black Hangman, and clear their own names of the murder charges. They are pursued to Africa by U.S. Army Intelligence officer Captain Ralph Carson (Regis Toomey).