YEONMI PARK: I didn't know it was even possible to sell humans. I thought people can only sell animals, chickens. But I didn't even know that kind of concept - human traffic - can be exist in the world. So I just couldn't process it when I heard it.

MARTIN: Hongwei repeatedly tried to rape Yeonmi. Each time, she fought back hysterically and threatened to kill herself. Finally, she made him a deal - if he could reunite her family, she would consent to sex. She was just 13 years old. Hongwei agreed. He bought back Yeonmi's mother, and he managed to help her father get out of North Korea and to join them in China. They all lived together in this strange and horrible arrangement. Months later, Yeonmi's father died of cancer and she and her mother pleaded with Hongwei to release them, and he did.

PARK: He let me go. That usually never happens. That never happen in China. He would send me to a farmer. He can make money. But he let me go without asking anything. I think because even though he was very evil, he had humanity inside of him and that was the reason why I can forgive him and I can see him as a human being.

MARTIN: Eventually, Yeonmi and her mother connected with a group of Christian missionaries who helped them travel to Mongolia, where they could claim refugee status. But it meant crossing the desolate Gobi Desert at night.

PARK: I heard about desert, but I never seen them with my eyes. I just couldn't believe there was nothing, except sand and except the stars in the sky. It was very cold - so, so cold that my even face was freezing. And I thought, what have I done so wrong that that's why I'm going through this? There's nothing I did wrong. I was just born in North Korea, and that was my crime.

MARTIN: Once in Mongolia, she and her mother flew to South Korea, which welcomes refugees from the north and where they could start a new life.

PARK: The first thing that I thought, like, freedom is hard (laughter) seriously, that really hard (laughter). I don't think I can do this. I didn't escape for freedom. I didn't even know what it meant to be free. All I wanted was food and safety. And I thought freedom meant was that you don't worry about getting arrested to wear jeans or watching movies or listening to music. I thought freedom was allowing me to do those.

MARTIN: She was overwhelmed with what she didn't know. The resettlement center taught her about the subway system and about ATM machines, which strangely spit out money. But what really threw her was the question that people at the center kept asking, what do you want to do with your life? She could not fathom having the freedom to choose.

PARK: Nobody asked me, what you think? Nobody cared what I thought in my life. And I didn't know that mattered, my opinion. And I said, why does it matter? Just tell me what to do. I'll do whatever you say. It doesn't really matter to me. And I really begging them, and I was hoping there was somebody tell me what to do with my life. So it was big lost. I felt lost there.

MARTIN: Yeonmi went to school, where she exceeded everyone's expectations, including her own. She gained confidence and started telling her story publicly. Yeonmi Park is now living in New York, studying English. She still has family in North Korea. And I asked her if she misses anything about the place where she grew up.

PARK: Human intimacy that I don't get to experience in this world. Because there was a - something indescribable closeness between humans, and I think there's no technology and there's nothing. So just we had to connect with each other. And I think those things that I'm missing the most.

MARTIN: Yeonmi Park now give speeches to crowded auditoriums in cities around the world. At age 21, she is a human rights activist on a global stage. When I ask her what she wants in her future now, her answer is a simple one.

PARK: I think everybody deserve to be free and to have a happy life. I wanted to show North Korean people that they have hope, and they can be free someday, like myself.

MARTIN: Yeonmi Park, her new memoir is called "In Order To Live: A North Korean Girl's Journey To Freedom."