>> again, that's something people wearing that go to bed. she was in the habit of only wearing it at night. >> the wedding ring left on the bathroom counter, a clunky retainer still in her mouth, added up, concluded a tech device, and you had a wife who never left a condo for her meeting that saturday morning. one who had never made it through the night alive, and the only person who could be with nicole pietz and the cause of the night, her husband, david pietz. >> when you look at each piece of evidence and figure how does it relate to everything else, put the puzzle together, and you've got your picture at the end. >> six years after nicole pietz was reported missing, her husband david was arrested and charged with second degree murder in connection with our death. >> coming up, a lifestyle on trial. >> he was trying to loosen her up to get her to do a threesome. >> when dateline continues.