With more than one million international students studying in the United States, some worry that intellectual property developed here is being stolen. NBC’s senior investigative correspondent Cynthia McFadden travels to China and to Duke University to investigate a case where a professor, who invented special invisibility technology, learned his Chinese grad student walked out the door with his research. The professor, Dr. David Smith, and the student, Ruopeng Liu, now a tech billionaire, sit down for exclusive interviews with TODAY.