MARY LOUISE KELLY, host:
To the story now of an unlikely spy. It begins in the West Bank in the '80s and '90s, where the Yousef family were like royalty among Palestinians because of this...
Mr. MOSAB HASSAN YOUSEF (Former Spy): We started the Islamic Revolution project as a family. That was our business.
KELLY: Mosab Hassan Yousef told me he was the prince of that family, the heir apparent. Yousef's grandfather was a popular imam. And his father - one of the founders of the militant Islamist group Hamas.
Mr. YOUSEF: And he inspires many Muslims around the world, not only Palestinians.
KELLY: You're the oldest son in your family. Was the expectation that you would follow in your father's footsteps?
Mr. YOUSEF: Yes, absolutely. Everybody was thinking that one day I would be the next leader.
KELLY: But Mosab Hassan Yousef didn't become that leader. He chose instead to give away Hamas's secrets, working as an undercover agent for the Israeli security service Shin Bet. It's a decision he explains in his new book, "Son of Hamas."
Your book opens, you were arrested, you were tortured, you say, and yet you were also at the same time approached. That was the initial approach by Israeli security, by Shin Bet, to ask you - will you work for us? Tell me, how did they do that? What happened?
Mr. YOUSEF: They offer everybody to work for them, including the terrorists. And I wanted to take advantage of that and take revenge from them. So this is why I agreed to work for them.
KELLY: So initially you agreed to work for them, but with the intention always in your mind of turning it against them and taking revenge.
Mr. YOUSEF: Yes, that was my goal, to be a double agent and take revenge from who tortured me, arrested my father, killed my people, and I thought if they trust me, it will be much easier for me to fool them.
KELLY: That was Mosab Hassan Yousef's plan. But meanwhile he was transferred to a camp with other Palestinian prisoners. Factions there were on the lookout for Israeli spies. They tortured those they suspected, putting needles under fingernails, burning off body hair. Watching that, Palestinians harming other Palestinians, Yousef, for the first time, began to see the world differently.
Mr. YOUSEF: Simply, I was very disappointed of the evil inside us. What is supposed to be between people I want to sacrifice my life for and my family dedicated their lives for and I found that they were torturing each other. It opened big questions in my mind, questioning if Israeli is really our enemies. I believed at that time, and I still believe that occupation is a problem. And every nation has its right to establish and decide their destiny. But we had enemies more dangerous than Israel, and those enemies lived within us.
KELLY: Shin Bet gave Yousef the code name Green Prince - green for the Hamas flag, Prince a nod to his father, a king within Hamas.
How did it work once you started working for the Israelis? Did they give you an assignment? What kind of information were you providing?
Mr. YOUSEF: In general, the Shin Bet give me lots of information. Since I'm the son of that culture, the son of that movement, I was born in the heart of the Hamas movement, and I had one of the best social networks inside this movement, which allowed me to be able to analyze any type of information.
KELLY: The Israelis also gave you money, paid for you to go to college, were very nice to you. I mean some people will look at this story and say you sold out. You sold out your people for Israeli money. What's your response?
Mr. YOUSEF: Yeah, if I was sold out it wouldn't take three years to end up really working with the Shin Bet. Second, if I sold my people out, why would I care about their lives? Many Palestinian leaders, they could get killed, and I was insisting that I cannot be a part of killing.
KELLY: You write that you tried to protect members of Hamas even as you were trading information with Israelis.
Mr. YOUSEF: Not to protect them. I wanted them to be behind bars. And I worked very hard to arrest them. So somebody who's really cheap to give information about his people for money, he wouldn't care about a human life, especially those people who want to kill me today, by the way. And if they discovered me, they would kill me without hesitation.
KELLY: Today Mosab Hassan Yousef has stopped working for Shin Bet, though he's clearly proud of his work with the Israelis. He does talk of his love for the Palestinian people, and for his family.
Your father is still alive, still a leader of the Hamas in an Israeli prison today. What was his reaction when you called? You told him yourself, didn't you, that you had been working for Israel all those years.
Mr. YOUSEF: He was silent. This is a huge shock for him. It's hard to believe. To be honest with you, what we did is much better than what Hollywood can do. We fooled Hamas. We fooled Israelis. We fooled the Israeli politicians. We fooled Palestinian politicians, everybody. Our goal, of course, was an open goal - to stop killing. But we had to fool everybody in order to do it.
KELLY: Was that your last conversation with him?
Mr. YOUSEF: I talked to him a few days before the release of the book. And I told him there is going to be a big storm. I asked him to disown me because I know that this is going to be very, very hard for him. He told me this is not an option.
He knows how much I love him. I really put my life at risk to protect him. He knows this in his heart. But what he doesn't appreciate, why did I go public with this, because this is very embarrassing for him. But I crossed all the red lines in order to open the way for other people not to be afraid, not to be ashamed of seeing the truth and challenge their leaders and their society.
KELLY: I should mention there's a final twist to your story, which is that you turned away from Hamas, also from Islam, and you've now converted to Christianity. You're now living based in California. Do you think you'll stay here in the States? Would you like to?
Mr. YOUSEF: I belong to that area and I hope that one day I will be able to go back.
KELLY: Go back home?
Mr. YOUSEF: Yes. I know this sounds impossible at this moment, but I love my country, the culture, I love the people. I'm not going to go to hide. I believe in what I'm doing. If the cost is my death, I will be willing to pay this, because, you know, I could be killed a long time ago for stupid reasons. So today, at least if I die, I will die for a very good reason.
KELLY: Mosab Hassan Yousef. His new book is "Son of Hamas." Read an excerpt at npr.org.