evidence we had because it showed he was still spying for china. >> finding the tasking notes in his trash allowed us to use more obtrusive investigate of tools. >> during this investigation, chi mak and his wife took three vacations which gave us opportunities to go into the home. the first opportunity, we went into the home and saw all the paperwork he had stacked up for work. the second opportunity we went in, we planted microphones in the house. the third time we went in is when we put cameras in the house as well. >> installing closed circuit television cameras was a challenge. you can imagine how well you you know your own room. to be able to go into that room and install something as invasive as the equipment needed to record closed circuit tv, it's difficult. >> you watch their daily life, what was going on at home. and how they dealt with each other as husband and wife was really unusual. we never saw an inkling of affection between them. there was no hand holding, pat