college student mackenzie lueck was diving into adulthood, eager to find her path. her family and friends knew her as fun, responsible and always careful. then one night, mackenzie vanished. a trail of electronic clues helped investigators retrace her steps and exposed a dark underworld were evil was hiding behind webs of lives. here's keith morrison with "the waiting car". >> our minds have a curious way of deceiving us. we sense something off, something wrong. even terrible. and yet, something in the brain wants to believe the worst didn't happen. kennedy stoner knows that feeling well. >> i was kind of pushing away from my gut instinct. i'm not really sure why. i never imagined this ever happening to one of my friends. >> i wouldn't think you would want to imagine it? >> no, or anyone that i know. so, my mind didn't go there. >> so, she told herself it would be fine, as she reached out from her home here in salt lake city, utah. messages to her friend, mackenzie lueck. >> i saw that she was an opening my snap chats and i texted her. i didn't get a text back. and t