Watch the program: Part 1 | Part 2

In May 2006, I read a fascinating article about the man (“CK” aka Kim Sang Hun,) who is credited with running the North Korean "underground railroad." The article names CK as one of Asia's heroes -– I decided to try get in touch with him.

Although I realized that making contact with someone like this is normally very difficult, I got in touch with a contact in Seoul, and he in turn used his own contacts to connect myself and CK through e-mail.

When I initially spoke with CK about my interest, he was uncertain about how we cover this story without putting the refugees about greater risk -- but through further e-mail exchanges, he agreed to meet me ... at a coffee shop in downtown Bangkok a few weeks later. A place so filled with crazed tourists, that a meeting like this would not draw any attention. This coffee shop is where we would have many subsequent meetings, all of them short and to the point. Each time we would discuss the logistics of our involvement with his operation, and we would then leave separately and go our own way.

The more meetings I had with him, the closer I felt myself getting to understanding how the railroad works –- and although I thought I was getting inside the operation, I did not yet have CK’s trust, and it would take many more months of meetings with CK, his counterparts, and North Korean refugees before I really understood the intimate details of how the network operates.

For the refugees, getting caught in China means getting sent back to North Korea to a certain prison term, and a possible death. For the aid workers, getting arrested in China means a lengthy jail term.

CK eventually agreed on the merit of our project, and agreed to help find a group that would allow themselves to be filmed. I took two initial trips up to China, in an attempt to meet the group we would travel with, and also to get an idea of the type of filming I would need to do. Security precautions start to become serious in China, and the humanitarian workers act very much like spies would -– codewords, fake names, no checking into hotels together, etc.

My first two trips took place in the middle of winter, and as Northeastern China borders Russia, it was very very cold. On my second trip, CK introduced me to a man who was trying to get his family out, a North Korean escapee himself, he was coming back to try to rescue his family.

But his family was still in North Korea, and as he was a former State Security Agent himself (SSA agents are the top level government security forces inside NK,) he was able to meet with some of his old colleagues, current SSA agents, and asked for assistance.

I was in the car for one of these meetings -– and the current agent, agreed with the relatives idea of trying to bring in a camera phone and get out video of the family. Cameras are banned inside, and the only way this agent was able to get the video back out, was to remove the memory chip from the phone, and tape it under his watch, it’s the only place security forces don’t check. The risk for him to do this was immense, getting caught would have likely meant a lengthy jail sentence for him, and his family.

I was filming in China as a tourist, as I never would have been able to get a journalist visa to cover a story like this. And I played the tourist, walking around in a sweatshirt and hat, as I filmed with a small consumer camera.

I waited in China for about three weeks –- but the family never came. We heard countless updates about their imminent arrival, but they never showed up.

As I waited, I had to keep changing hotels every two days for security precautions. Eventually I had to pull out of China and go back to Bangkok. I was still very interested in continuing with the story, but I had to understand the reality that family might likely never show up.

Over the next few months, I continued to hear updates about the family. I was told on countless occasions that "D-day is tonight," but for a variety of reasons they never showed up.

But one day in early May, I got a call from CK, "believe it or not, half of the family has arrived, and the other half will be coming soon," he said. I packed my bags and flew back up to Northeast China.

The family had in fact arrived, and we spent the first night filming with them in a hotel room from 1 a.m. to 4 a.m. They were painfully nervous about the trip, and told me very quickly that if they caught they will be executed -- Instead of getting sent back to North Korea, their plan was to commit suicide. This immediately brought the reality of the situation to the forefront. These people wanted freedom, and they were risking their lives to get it.

I spent the next three weeks on the underground railroad with them, a journey of roughly 5,000 miles -- traveling by bus, train, taxi, motorbike, and by foot. We went from safe house to safe, from border to border. I was lucky enough to be able to film the entire journey -- speaking with them about their feelings at each moment, filming them getting sick along the way, and rejoicing when they got onto Thai soil.