<p>When Clint Haines last scoured the highlands of central Vietnam, he was part of a US Army "hunter-killer" team, an airborne cavalry unit that swept low over the treetops, drawing fire from an invisible enemy and calling in strikes on hidden encampments. Thirty-two years on, Haines has returned to his old battlefield with the same stomach-churning, heart-pounding thrill of mission he felt every morning he boarded his helicopter in 1971. Only this time, Haines is not hunting for Viet Cong -- he is searching for the child he fathered and has never known.</p>