Transcript for Parents Who Found Missing Daughter on Backpage Fight for Justice: Part 1
Good evening, there is explosive new evidence in the investigation into a website accused of enabling the trafficking of under-age girls. For over a year now, our own ABC news investigation has taken us through a sordid world of young girls for sale, and the efforts to stop it. This week, a major breakthrough with the senate finding evidence that the executives of back page douk were not only aware that minors were being sold for sex through ads on the site, but went to lengths to hide it. Here's ABC's Gloria Riviera. How are you doing? Reporter: For parents Tom and Nicole, it's a long awaited day of reckoning. Good to see you. Reporter: They've come to the capital for a major hearing. It's time to accept that child sex trafficking has entered the digital age. Reporter: Targeting back page.com, the controversial website they say destroyed their daughter's childhood. Back page is a $600 million company, built on selling sex, and importantly, on selling sex with children. Reporter: The company's suited executives forced to stand and listen to a damning indictment on a national stage. Those children were still sold! They just tried to sanitize it. That, ladies and gentlemen, is the definition of evil. Simply evil. Reporter: I first met Tom and Nicole last spring. Yeah, they took everything from my little girl. When I grow up, I'd like to be a doctor. Reporter: Just a few short years after that video was taken, Tom and Nicole's ten 15-year-old daughter who we'll call Natalie, would be sold for sex to the escort listings on back page.com. How many encounters do you think you had during that time? Over 150. Reporter: Over 150? Yeah. Reporter: What would have been possible without back page? No. Reporter: A high school freshman, she got a bad grade in school and decided to run away. Never suspecting that a childish rebellion would lead her on a dark path, into the hands of a pimp. What did he say to you about back page? He said it's safer. Said, it's easier not to get caught. Put me in all these clothes. Took some pretty provocative pictures of me. And then, go to back page and you can click on to post an ad. Reporter: Back page say basic classified ad site with racy sections for escorts and body rubs. Technically, what law enforcement calls thinly veiled code for prostitution. He started getting physically abusive and he would sleep in the living room next to the front door, so I couldn't, like, leave. Reporter: How often did you work? Every single day. It's too simple. Ask you if you're 18 or older. A simple yes click was about as far as that went. Reporter: Whoever owns back page, he's got to go home at night and know he's selling kids today. He's just as accountable as the pimp that sold her, in my mind. Reporter: In the past, many have filed lawsuits claiming back page facilitates prostitution. But a law protects the site. I think the most important parts of the communications decency act, it protects freedom of speech on the internet. If you have someone selling a stolen car on your website, and you don't know that the car is stolen, you are now not responsible for the selling of a stolen vehicle. You're not liable for what's on your site? Is that one way to interpret it? You really aren't necessarily liable for the postings of other people. Reporter: And so the dallas-based company flourished, worth an estimated $500 million. While CEO Carl Ferrer and other back page top brass have remained out of the public eye. Last year, we decided to investigate back page. After talking to Natalie's family and others who have lived through the same nightmare. Who weren't yet ready to step out of the shadows. So between her going and you finding crystal's photo on back page.com, how much time? About 48 hours. But I remember that she had on the -- the see-through lacy teddy. Reporter: She's 14. And she's 14. I called the cops and told the cops what was going on. Reporter: What did you tell them? I told them my daughter had been posted on back page and that she was only 15. They needed to do something, they had to go get her. Reporter: We teamed up with Seattle's vice squad to find out how simple it was for young girls to be sold online. This detective created an ad for an 18-year-old girl with the mention of a younger friend. And here's the kicker. Ask about my younger friend. Reporter: Within minutes, the ad was up and running. It's essentially advertising an under-age girl. Oh, my god. We've gotten several phone calls, several texts. They're really coming in. Hey beautiful, are you angel? Right then, it's another one. It hasn't even been up for half an hour. This is crazy. Reporter: This post actually led to a real-life arrest. Stay here, stay here. He tried to bolt. Police, you're under arrest. Tactics like this are becoming common place across the country. Back page did tell us they make sure to cooperate with law enforcement investigations. Ready? Is there splinters in there? Reporter: But for girls like Natalie, it's not about catching Johns, but holding the men behind back page accountable. We followed the paper trail to Amsterdam, the red light district and legalized prostitution, looking for CEO Carl Ferrer. Reporter: We're in Amsterdam, did Carl Ferrer own any companies in Amsterdam? We discovered Ferrer seems to be running a few other escort websites from here, including a site called cracker, available nearly everywhere except the United States. Reporter: Carl Ferrer has turned down several of our interview requests. We've come to this hotel in Amsterdam, because we found out there's a conference Carl is scheduled to attend. Turned out, he's an active member of the classified ad industry. It's a chance for me to talk to other CEOs in the industry and share ideas. Reporter: He attends a networking conference every year. It doesn't take long before we spot him. Carl? Carl Ferrer? Yeah. I'm Gloria Riviera with ABC news. We just want to ask you a few questions. I'm fine. Law enforcement tells us that under-age girls are trafficked on your site, back page.com. I'm sorry. You're a father. He wants to know why this is going on. What would you like to see in an ideal world happen to back page? I think they're guilty of a criminal act. And it's reprehensible what they're doing. They're selling kids. They know they're doing it. They justify it. And they should be held accountable for that. All of them. Mr. Ferrer, you're charged with ten counts -- Reporter: And back in October, the state of California tried. Ferrer and co-founders were arrested and charged with pimping. The first time they've faced criminal charges. In the courtroom, back page's lawyers again argued that the charges were in violation of their first amendment rights. It's already a situation where the rights of these defendants individually have been harmed considerably. Reporter: And the judge sided with back page's defense, dismissing all charges, citing the communications decency act. They've touted their system for screening their adult ads, employing moderators, a filter for key words. In 2012, their attorney told "Nightline" -- Online child exploitation exists, and the best tools to fight it are also online. And back page.com is currently one of the very best tools to fight it. Reporter: Claiming they report suspicious ads to the national center for missing and exploited children. Back page maintains it has monitoring programs and it also told "Nightline" that back page is online to fight human trafficking. I don't think you can be in the business of providing basically an online bazaar for escort ads that includes of purchase and sale of children for sex and say that you are online to help fight the problem. Reporter: In fact, 73% of the reports they receive from the public about suspected under-age trafficking involved a back page post. Which is why two U.S. Senators have made it their mission to uncover the truth. I'm betting, when we get all the financials, they're not making much money selling motorcycles, but they're making a whole lot of money selling children. Reporter: When we come back, the new explosive revelations from internal company documents. These are the practices of a corporation intent on profiting from human trafficking and human misery. Is this the turning point that Natalie and her family have been waiting for?
This transcript has been automatically generated and may not be 100% accurate.