IT WAS AFTER 10 P.M. on July 8, 2009, when Sandra Mansour answered her cellphone to the panicked voice of her daughter-in-law, Nasreen. A week earlier, Nasreen and her husband, Naji Mansour, had been detained in the southern Sudanese city of Juba by agents of the country's internal security bureau. In the days since, Sandra had been desperately trying to find out where the couple was being held. Now Nasreen was calling to say that she'd been released—driven straight to the airport and booked on a flight to her native Kenya—but Naji remained in custody. He was being held in a dark, squalid basement cell, with a bucket for a bathroom and a dense swarm of mosquitoes that attacked his body as he slept.