John Bul Dau, 34
Syracuse, N.Y.

Other than memories, all John Bul Dau has left from his childhood in rural Sudan is a line of tiny scars on his shoulders. When he was a young boy, a traditional healer treated him for typhoid by placing red-hot metal balls on his feverish body. "Your skin smoked," recalls Dau as he discusses his plans to aid his home village. "If I can build a clinic, people will never have to do that again."

When Sudan descended into a horrific civil war, archaic medicine became the least of Dau's worries. As a young teenager, he fled a government militia attack on his village, joining thousands of other homeless Sudanese boys on a harrowing 1,100-mile trek to safety. Granted asylum by the U.S. in 2001, he now costars in God Grew Tired of Us, a documentary coproduced by Brad Pitt and narrated by Nicole Kidman that tracks him and other so-called Lost Boys of Sudan from their ordeal in Africa to the challenges of adjusting to America's mind-boggling plenty.

The grateful Dau is determined to give back. A longtime leader and advocate for some 4,000 Lost Boys and other Sudanese refuges in the U.S., Dau has raised $180,000 to break ground this month for a medical clinic in his home town, whose villagers currently must walk 75 miles to see a doctor. Dau is "a born leader," says Jack Howard, a member of the First Presbyterian Church in Skaneateles, N.Y., which sponsored Dau's resettlement in nearby Syracuse and is helping organize fund-raising for his clinic. "A lot of the Lost Boys want to help their people. John knows how to execute."

He has already conquered nearly unimaginable challenges. In his teens, wandering with the Lost Boys from southern Sudan to the border of Ethiopia and then to Kenya in search of safety, he survived disease, starvation, thirst, militia attacks and hyenas. Six-foot-eight and rugged, he became a leader to hundreds of younger boys, many of whom died. "We chewed the grass. We drank mud and urine. It was a very bad life," he says. More than 20,000 refugees reached a makeshift camp in Ethiopia, where cholera and measles soon spread. The survivors journeyed in 1991 to shelter at a refugee camp in Kenya. By the time they got there, their numbers were halved.

Dau set off on another journey in 2001, when the U.S. offered asylum to some of the refugees. Aboard his first airplane, "all I could see were lights everywhere," Dau says of landing in New York City. "I thought, these people must be so rich. The lights looked like a huge grass fire."

In Syracuse and their other new American homes, Dau and his compatriots needed lessons about every aspect of modern life, from indoor plumbing to refrigerators. The change in diet proved particularly tough: "When we first got here, we ate doughnuts, and that smell stuck in my mind," says Dau. "I couldn't eat them again."

After juggling a number of jobs to get on his feet, Dau now works as a hospital security guard and attends Syracuse University, hoping to get a degree in immigration law so he can help other refugees. He has also reconnected with his family—and started one of his own. In 2002 Dau, who believed his parents had been killed, came home to find a letter from them, alive in a refugee camp in Uganda. On the telephone, he spoke to his mother for the first time in 15 years. "She said, 'I don't believe you—you don't sound like my son,'" he says. "And I said, 'I am your son, but I am not the boy you remember. I am a man now.'"

Two years later, he got permission to bring his mother, Anon Duot, 66, and a sister, Akuot Leek, 18, to the U.S. In 2005 Dau returned to Africa to ask relatives of Martha Akech, 24, a woman he met in the Kenyan camp, for her hand in marriage. Using his work savings, he paid a traditional Dinka dowry: 80 head of cattle. The couple had a baby daughter, Agot, in November.

The soft-spoken Dau sees the source of his determination—to survive and to help others—as simple. "You can't always expect God to make things easy," he says. "I didn't give up."

Know a hero? Send suggestions to HEROESAMONGUS@PEOPLEMAG.COM Please include your name, phone number and return e-mail address. For more information on Dau's work, go to www.directchange.org/sudan