Using Wu Tan's advice on how to endure pain, Jack (Tom Brown) makes it across the pit of hot coals unscathed and is assigned by Lo San (Nigel De Brulier) to return to Chunking with the Mandon Secret. In Chunking, meanwhile, Fraulein Von Teufel (Rose Hobart) arranges for the Japanese bombers to strike her own secret hideaway at a predetermined hour. Arriving at general Kai Ling's (Sidney Toler) headquarters with the Mandon Secret, written in invisible ink, Jack is called to Trudy's hotel room. There, the reporter reveals herself to be Fraulein Von Teufel and informs a none too surprised Jack that she has captured Tommy (Edgar Barrier), Janet (Marjorie Lord), and Captain Wing (Keye Luke). Jack also has a revelation, however. The paper with the invisible ink was a decoy and the real Mandon Secret is arriving with Wu Tan (Philip Ahn). Joining his captive friends, Jack manages to free himself just as the Japanese bombers strike. Happily, the little group makes it out of the building alive, but Fraulein Von Teufel, who has been double-crossed by the wily Kageyama (Turhan Bey), is not so fortunate. The Black Samurai organization destroyed and the secret route to India safely in the hands of the Chinese government, Jack receives a commission from the United States air force. ~ Hans J. Wollstein, Rovi