welcome to "dateline." 20-year-old lynsie ekelund and her mother told each other everything. when the college student vanished out after a night out clubbing, nancy thought she was at sleepover with friends and that wasn't the only secret lynsie was hiding. it would take years for detectives to uncover the truth, buried in a pile of lies. but could they find lynsie? here's josh mankiewicz with the night lynsie disappeared. sometimes the facts are as clear as the southern california sky. but other times you have to know where to look. to see the truth. this man has made a career of noticing what others do not. what's his reputation? >> meticulous investigator. just pours over the volumes of evidence and finds things that others do not find. >> the evidence whisper per. >> right. >> does this man act guilty, does he know more than he's saying? >> i didn't know anything was going on. all right? i just was like, where's lynsie? >> what about this man? can you believe the story he's telling? >> i was supposed to pick her up twice. she didn't show up on either day. >> the evidence w