nailah. no one. nailah's sister kept replaying their last conversation. >> she called me, and she said i've got something to tell you. and before she could tell me, she got a call on the other line and she clicked over and she said she'll call me back. >> she didn't call you. >> she didn't call me back. >> awful what a person's mind could churn up in the dark as day one became two and then day three. >> i kept calling her. and kept calling her. i kept thinking she's going to answer. she's going to answer. she's going to answer. >> there's no handbook for this so you wake up and think it's a bad dream and no, it's still real. >> the case of the missing pharmaceutical representative landed on the desks of sergeant mia oliori and detective greg jacobson who, right away, scanned nailah's phone records and found something alarming. just after 10:00 p.m., the night nailah vanished, her cell phone made three calls to 911. >> chicago emergency. >> no voice, no struggles could be heard. no background