Tonight we're going to bring you a really powerful and eye-opening report that might challenge everything you think you know about prostitution. It's the latest in our series "Hidden America." And I'm... See More
Tonight we're going to bring you a really powerful and eye-opening report that might challenge everything you think you know about prostitution. It's the latest in our series "Hidden America." And I'm here with our colleague Diane sawyer. Welcome back, Diane. So great to see you, juju. It's always great to have you on "Nightline." But I know this is also a story that we both care very deeply about. We have covered it over the years and we've talked about it all around the world. But tonight, sex trafficking, something happening right here at home. Our colleague nick Kristof of the "New York times" and his wife Cheryl wudon have made a remarkable documentary called "A path appears." And they have been following women, often very young girls, locked into a life of prostitution by highly skilled profiteers, pimps. And you're going to hear nick argue when you look closely these women are in fact not criminals but hostages walking among us. By night and by day across the country young American girls controlled by pimps are sent out to have sex for money. Sometimes 20 men a night. You had to make at least $1,000 a day. There was no days off. You had to sleep with 10 to 20 strangers per night. I'd probably have up to like 20. I was so exhausted. I didn't want to do it anymore. He hit me a few times. And then he had a gun and he'd point it at me and he was like, you need to do what I say. He was like, I will kill you. Reporter: Savannah was looking at websites when she was lured away. A study says the average age a girl enters prostitution is 12 to 14 years old. So one day I think I was 13. I didn't really know a lot about anything. I went online and I wanted to -- I don't know how I came across like this website for like -- you know, like sugar daddies. I didn't know that I would have to have sex with them. I just thought they were going to -- I don't know what I was thinking. But I just thought that, you know, they would buy me stuff just because I was pretty. I don't know. I still did not understand what was happening, like completely, even though I went to the hotel room, until it happened. Reporter: And that is just one way pimps lay the trap. Again, it's not that bad. Reporter: At New York's port authority two plainclothes officers, sergeant hector Martinez and officer jack Collins, tell me we are surrounded by pimps just out of sight who come here to stalk runaways. The pimps can spot them immediately. You're in a kind of race against pimps. Absolutely. The greyhound. Wannabe pimps, recruiters. Now, they watch. Reporter: The officers try to intervene. A lot of the kids are from foster care. A lot have been sexually abused. And the predators know exactly what they hope to hear. They sell them on the idea of a warm place to stay for a night. The possibility, potential for romance. Maybe earning some money. Reporter: So these officers may be the last chance before a girl disappears into the shadows. Maria has been looking for her daughter, who ran away when she was 15. I haven't heard from her. Reporter: In this documentary "A path appears," nick yiftoff continues his lifetime mission, going in search of missing girls. With an anxious mother looking on, he searches some of the websites where the girls are most often advertised. He spots a picture and the offer "Mixed Latina catering to your needs." There's a mixed Latina catering to your needs. Emily. Can you click on it? Yeah. Do you recognize -- Yeah. Well, let me see and then I'll I'll -- maria. Maria. That's her. You have to make sure. Oh, . Okay. That's her. Oh, my -- Okay. Now we found her. We found her. But listen. Now we have her. Now we have her. . We found her. What happened with these men? Will we find them too? As he continues his search nick tells maria her daughter has been trafficked in more than one state. So she was taken to new Hampshire as well. And there's another girl with the same phone number. At least one. Maybe a couple. So it's evidently somebody who's running a couple of girls. And you know. Reporter: It's big business. A pimp can pull into a truck stop with an rv full of seven girls and make $1,400 an hour. This fundamental misperception that somehow a pimm. And this girl are dividing up money or something. Every penny she earns goes to the pimp. Every penny. And if she holds him back or she doesn't meet her quota that she is given, whatever, $700, $800 that day, then she is going to be beaten up. Reporter: In the documentary a former young girl on the street named Shawna drives her car to an area she knows is frequented by pimps. One pimp used to call her shelly money. You remember me? Yes. Who am I? I don't remember your name. Shelly money. What are you doing? You got a girl out here? Three? Three girls. You waiting on one to come back now? Yeah. Reporter: In the car with her, a long-time activist, actress Ashley Judd. How much do you expect her to bring? 40. No less. So if she comes back with more than 40, do you expect she'd be up front with you and give you the full or is she only going to give you 40 because that's her minimum? I'm taking care of her. A room and a place that's safe to stay. And drugs. So you know. The one you're waiting on now, what's her habit? Crack. Everybody's using crack. Everybody. So you supply her dope? And if she comes back with less than 40, I mean, god forbid, what's going to happen? I've got a different system than other people. I try to treat them right. Like in the morning they want to eat. I give them a v-8 or Orange juice. Reporter: As we said, it's big profit, supported by the thousands of men buying sex every day. The chance that any one of those is going to be arrested is infinitely lower than the chances they'll be struck by lightning. Reporter: Last year in one New York City court more than 400 charged with prostitution offenses but only 10 accused of being pimps or Johns. In 19 states they tried something different. Highly publicized stings on the Johns. This is Chicago, cook county. Predictably, the men arrested say this is their first time. First time. First time ever? Or first time getting caught? First time ever. How many times per month do you think -- would you say you do this? Never. There's not really a demographic. You know, occupation, doctors, lawyers, police. The sheriff says he always asks the men a memorably trick question. Would they like to avoid the fee for having their car towed? One of the things we always offer them as opposed to the $500 fee to get your car back, we'll allow you to call your wife and have her pick your car up. And not one has ever taken us up on it. Reporter: So in cities across the country thousands of young girls are at the crossroads. We're back at New York's port authority, where the predators are stalking. I see a girl alone, wonder if she's okay. I'm looking at that girl over there. Give me a sec if you want me to go do my thing. Sure. Why not? Hey. How are you doing, hon? I'm sorry to bother you. You're not in trouble or anything. Thank you very much. I really appreciate it. Reporter: Her I.D. Says she is 19. Older than she looks. And she says she has a job at the terminal. But for these two officers a night has just begun. Last year 69 runaways were pulled to safety. One to three runaways a week. And most of those would be trafficked if you hadn't intervened? Absolutely. Either they're about to be trafficked, they are being trafficked or they're out there living the life. Reporter: Around the corner from the port authority, covenant house, one of the largest shelters for at-risk youth. Jane biggleson says she hears from the girls who fell victim how easy it was. One person says he was the first person ever to give me a birthday cake. He was -- they know what the young person needs. If they were gun traffickers out there, we would find ways to get them out of the picture. But somehow if it's people who are trafficking 15-year-old girls then somehow that's not enough of a priority and so we regret it but they're still out there. Reporter: Covenant house tries to provide housing, therapy, the real help in life only promised by pimps. These are homegrown American girls. It's basically seen as a public nuisance issue rather than as a human rights problem. Reporter: Shawna, who started at age 14, remembers the day she couldn't take it anymore. She says after 22 years she was here, waiting above a filling station. You know, I was so tired. And I was like, if you are a god, save me. I walked back out to the road right out there and the police picked me up and took me to jail. And I was so tired I just couldn't do it anymore. Reporter: As she's driving she sees a woman she recognizes on the street, someone who was also once young and had a different life ahead of her. Clean for three years now. Well, I'm not. Get away from me. When you get -- I'm not a ho no more. When you get tired, let me know. What's your number? 320. I am tired. Are you tired? Yes. Are you ready to go today? No. No? I'm tired. I want to get well. Go on. I love you. I've been there. I know. God. She used to be so beautiful. ? I don't know an easy way to walk away ? And beautiful as the young girls back at home tonight. The mother whose daughter was seen on that website. And that young girl who didn't know it would be about sex. I love you. Who found her way home to her mother. And as beautiful as the young girls still lost in the shadows. And nick Kristof's documentary "A path appears" premieres on pbs Monday night, juju. Thanks so many, Diane. A remarkable piece of reporting.
This transcript has been automatically generated and may not be 100% accurate.