It was known as "The Great Escape": 76 Allied prisoners of war, desperately crawling to freedom through a man-made tunnel. Within days, 50 had been brutally murdered by the Gestapo - a blatant breach of the rules of war. Meet the investigators who searched the globe to bring these murderers to justice, many of whom claimed they pulled the trigger solely to save their own lives. Join us as NGC reveals the untold story of one of WWII's most astonishing criminal investigations.