Private McKinley Nolan vanished forty years ago in Vietnam on the Cambodian frontier. Some say he was captured, some say he was a traitor, some even say he was an American operative. The U.S. Army officially claims he was radicalized and "went native," joined the Viet Cong and was later murdered by the Khmer Rouge. In 2006, retired U.S. Army Lt. Dan Smith, revisiting the battlefields of his youth, may have encountered McKinley, alive. So begins a journey into the heart of darkness.