"These Arabs go into the north and purchase, steal or help runaway slaves," Williams says. "We pay the raiders 50,000 Sudanese pounds for each slave they redeem. On this mission, we liberated 4,435."

This method of purchasing freedom began in 1995 when the Dinka people asked CSI for help through the Sudanese Council of Churches.

The slaves are brought to different sites throughout the border area where the organization fingerprints and photographs each one after paying the Arab redeemers a flat rate for their service.

It was Williams' job to record the slaves' stories. Using a translator, he interviewed about 25 people.

"In not one of those interviews did I see a tear from any of them," he says. "They had resolved to fight and to remain true to their people and their faith."

Williams says even as the former slaves were told that they were now free, many showed no joy at the point of liberation.

"They were confused and had been lied to so often," he says. "But then when they were united with their family members, they were able to let their emotion show."