For Kenya's police force--struggling to keep the peace in a nation traumatized by post-election violence that tore open ethnic fault lines--a handful of middle-aged mothers from the slums of Nairobi make a strange sort of target. "We are Kenya's four most wanted," said a 43-year-old woman who sells traditional wrap skirts for a living. She called herself Mary, saying the police would come for her if she gave her real name.