The frantic international search for the young American mother who suddenly vanished while traveling alone on a dream vacation. It was her first trip overseas but right before she was supposed to... See More
The frantic international search for the young American mother who suddenly vanished while traveling alone on a dream vacation. It was her first trip overseas but right before she was supposed to return home to her husband and her two young boys in New York. She disappeared. Without a trades. NEC's Yu Chang brings -- the latest. What -- was the trip. A life time complete with -- instant Graham post from Istanbul -- -- Sierra an avid photographer shared with her family back home in New York but when her family went to -- grabbed the airport a week ago. They discovered to their -- that somewhere halfway around the world. She simply vanished -- United Airlines. They stated that she didn't. She didn't board the flight tonight her husband Stephen is caught up in -- gut wrenching global missing persons case. You know -- so many stores are going to remind you don't know what to think you don't know what to believe. You know what to expect you know what's gonna come out of this. It was a dream vacation she'd planned with a friend who dropped down at the last minute. Her family says Sierra had every reason to come home -- even -- trip short can she missed her eleven and nine year old son's. And she was eager to register for new classes at a local call each I've been married to -- fourteen years. And my love -- is -- is deeper than I've ever have for any other individual. Tonight these grainy surveillance videos released by Turkish police could be the best lead investigators have. As they scanned for clues to the 33 year old mom's disappearance. Nothing seems -- as she walks around -- mall. Eats alone in -- food courts. Eerie images taken a day before she lost touch. What she's seen having coffee with somebody is there any surveillance of somebody walking in or out with up with her at a location. All of those -- potential -- The mystery deepens because Sierra stayed in Constant Contact with her family through Skype an instant messages. Her last -- was received last Monday saying I'll be home tomorrow yeah -- And then. Digital silence. At the hostel where she was staying Turkish police found her clothes her passport even -- medical cards and phone chargers still in the room. The owner told authorities he last -- Sierra Sunday afternoon. With her passport in the room. And I've heard even herself on was in the room. I don't like that combination because that. It leads me to believe that someone. Was able to lower her out of the room. Stop I want to the yeah. Like the storyline seems like something out of a Hollywood movie with -- taken and taken to which she takes place in Turkey -- derided disappeared. Stars -- Neeson as a father trying to rescue loved ones who get kidnapped kind of in human trafficking. -- -- But that is more likely the stuff of entertainment according to former FBI investigator Brad Garrett. Television tends to drive people toward the sex trade that someone could -- Is that possible I suppose it is I would focus on. -- are the sex offenders or people who have had histories of abducting women in and around Istanbul in the areas where she was frequently. At this point every clue is precious go through her camera what -- the last shot she had taken that may give you a direction. But investigators will probably want to talk to surprise husband -- brother both of whom are now in Turkey working with authorities. The US State Department refused to comment other than to say they too are working the case with Turkish national police. -- -- with families going through they are. Trying hard to. Do the right thing in hoping that there's somebody who's going to tell them. Here's what we need you to do -- done savage his brother Joseph went missing in Honduras back in 2009. Essentially he went on a boat and disappeared. Whether or whether it was a matter of getting caught in -- -- current had a heart attack or. It's equally likely that somebody decided they wanted the vote but you'll never know where we we will likely never now. Jeff went into enormous debt searching for his lost brother. And now runs a web site that connects families and gives advice. The site has hundreds of registered loved ones looking for the dozens of people who seemed to have dropped off the face of the earth. While visiting exotic -- it's. There's a language barrier there's a cultural barrier it must be very difficult to get an investigation. Underway or -- -- in South Shore again that's where you think the State Department will be of a vital systems and for the most part they're not there of their their very quick. To tell you the limitations on what they can do there's a little bit of blame the victim that goes on in this situation isn't there yet that happens a lot -- -- and the fact that you that the the first place you start seeing it is if there is news coverage if you're fortunate enough to get news coverage to build awareness of abuse situation. Immediately the Internet trolls are. On there commenting. With tough things about. Doesn't -- must must not want to be found must've been up to no good in and got some you know something they had coming to them. It's -- that's probably the most heartbreaking -- hope can be painful. Perhaps the only thing more painful is having no hope at all for Nightline I'm juju Chang in New York.
This transcript has been automatically generated and may not be 100% accurate.