Tonight we're taking you inside the dark arts of hostage negotiations. With someone who knows them all too well. Kidnapping is a booming criminal enterprise and you're about to meet a mom who lived... See More
Tonight we're taking you inside the dark arts of hostage negotiations. With someone who knows them all too well. Kidnapping is a booming criminal enterprise and you're about to meet a mom who lived every parent's worst nightmare when her journalist son was taken by terrorists. So how did he get out alive? Here's ABC's chief investigative correspondent Brian Ross. My name is peter Theo Curtis, I'm a journalist from the city of Boston, Massachusetts, usa. Reporter: A hostage video sent by Al Qaeda in Syria. And the beginning of a two-year nightmare for freelance journalist peter Theo Curtis and his family that has now finally ended with his release. He's been through so much. So many terrible things that I don't know about and don't really want to know about. Reporter: Today, Curtis' mother told Amy row back of ABC news about the agonizing months when she did not know what would almost to her son. Those days had to be excruciating. They were excruciating. It was a real roller coaster. But I was getting words of reassurance if I didn't hear something of course I would worry maybe something would go wrong. But -- you know. Theo's case, it turned out all right. Reporter: Al Qaeda and other terror groups have turned hostage-taking into a thriving business, putting the captive's families, their employers, and their government in the difficult positions of negotiating with people who put little value on human life. If you accept the demands I live, if you don't accept the demands then I die. I think most people would say, I value life, I want to get them out, I'll do what I have to do. And please help me. And that's what we do. Reporter: Former FBI agent jack clunin works as a full-time negotiator who's helped gain the release of more than 150 kidnap victims including one european journalist held by Isis. There is reason to negotiate with them, you can talk to them, and you are going to be treated very badly on the phone. You are going to receive e-mails, you're going to receive videos, you're going to do everything that you possibly can do to keep that information stream alive. Reporter: For the european journalist who had been set free by Isis, clunin says the average ransom is about $2 million in cash, U.S. They don't take a wire transfer, they don't take credit cards, they don't take euros. They want cash. But you are held at their mercy. So imagine trying to move a sum of money around like that in a war zone. Reporter: He says the actual exchange with Isis often takes place near certain border crossings with Turkey. This is an expanse of territory that's basically considered no man's zone. Then you're going to have to move them probably under the cover of darkness, which they control. Reporter: In the case of James Foley, Isis made a ransom demand of some $130 million. Plus the release of certain Al Qaeda pricer ins. He says Isis wants more than ransom for its American hostages. Let's be brutally honest. This is a game of revenge. And revenge is sweet to them. And they want to take it. We are in their minds the worst people on the face of the Earth. Reporter: British authorities today were focusing on neighborhoods in London where several hundred young Muslim men have been recruited to become some of the most brutal jihadists in the Isis organization, including this man. One-time rapper known on youtube as l-ginny whose father is awaiting trial in New York for the Al Qaeda attacks on U.S. Embassies in after that. Two weeks ago there was this el ginny posting showing the severed head of a Syrian soldier saying "Beheading is the only cure." The only source of identity is a very extreme and arguably manipulated version of Islam that says, I don't belong to any nation, I'm only loyal to Islam, and America is our principal enemy. Reporter: British authorities don't believe the rapper was the executioner of James Foley but they say they are close to figuring out who he is. Starting with the eyes of the hooded man, advanced facial recognition experts created this likeness of the possible killer. Clean shaven, then with a moustache. Whoever he is London radical Muslim cleric says Foley's death could have been prevented if the U.S. Had negotiated with Isis over the release of prisoners held by the U.S. His life could have been saved. However gruesome it may look, however much it may have shocked the world, the fact is they're the circumstances and we can't ignore those. Reporter: With American journalists held hostage by Isis the debate has been raised anew about whether to negotiate with terrorists. It's the code of honor. If we ask people to do extraordinary things, if things go wrong we have to do extraordinary things to get them back. Reporter: ABC news foreign editor John Williams dealt with the issue when he worked at the bbc and helped gain the freedom of bbc correspondent Alan Johnston in gaza. They said he'd been executed. He hasn't. But they said he had been executed. And so when eventually a video emerged of Alan, we were thrilled. They've fed me well, there's been no violence towards me at all. Just to see him alive? Because we had convinced ourselves and his parents had convinced themselves that he was dead. So everybody thinks the hostage videos are a terrible thing. Actually, to those who are closest to the kidnap victim, they're proof of life. Free Alan now! Reporter: As Johnston spent almost 114 days in captivity, the bbc negotiated online. It turned out the message was coming from an intermediary sitting in Germany. He was talking to us and talking to the kidnappers. And then channeling the messages from one to another. Reporter: Ultimately, the bbc reporter was freed. But only after the terror group hamas interceded on his behalf. For the last week I've thought of very little else, that hall LAN was kidnapped for 114 days, Jim felly had been in for nearly two years. I think it's hard to overstate the burden that that puts on someone who is living through a kidnap. Reporter: A burden at least three more American families are facing tonight. For "Nightline," Brian Ross, ABC news, New York. And our thoughts go out to those families tonight. Thanks to Brian Ross for that report.
This transcript has been automatically generated and may not be 100% accurate.