Even at 64 years old and in failing health, James Dresnok projects an imposing figure. Six-foot-five with a huge frame and giant jowls, he speaks into the camera with a firm, distinct Southern accent. Metal teeth glint as he talks. “I will give you the truth; I’ve never told anyone before,” says Mr. Dresnok, a former soldier, a defector and, for the last 44 years, a resident of Pyongyang, North Korea. Mr. Dresnok is at the center of Daniel Gordon‘s documentary “Crossing the Line,” along with the stories of three other American defectors who crossed the 2.5-mile, landmine-strewn demilitarized zone to live in North Korea. Mark Russell reports.