The Two Headed Spy (1958)

World War II spy thriller supposedly based on true story. A British secret agent successfully infiltrates Nazi military and achieves the rank of General during World War II. He gains full confidence of entire Nazi high command, including F├╝hrer Adolf Hitler, save one suspecting German officer. All the while, the spy passes war-winning information to Allies assisted by two loyal Berlin contacts, first a man, then a nightclub singer. A war drama with love-interest relationship and a cliffhanger finale. Also memorable is frightening Adolf Hitler always portrayed from behind, face unseen, but with snarling, tyrannical voice.