Back at Harvard, Williams has been doing his best to spread the word about his mission. He hopes to share his story at a Senate hearing on slavery next week.

Williams says he is especially disturbed by U.S. government's silence on the issue of slavery in Sudan.

"[Secretary of State] Madeline Albright has said that the issue is not marketable to the American people," he says. "But I think if our government is made up of leaders then that's what they're supposed to do--lead. They shouldn't always wait for the groundswell of public opinion."

Williams says the United Nations has been critical of rescue missions like the one he participated in because the UN does not agree with the idea of purchasing freedom.

But Williams argues that since the Dinka people sanctioned the missions and slaves are redeemed for a flat rate, many of the UN's fears are misguided.

But even if their criticisms were true, Williams says, no one else has given an alternative solution.

"Redemption missions do not solve the problem of slavery," he says. "But since they began, 38,000 people have been reunited with their families. I think that definitely justifies the work that we do."