If the preachers who spread their message on the banks of the Congo are to be believed, the face of evil is found in the despairing gaze of an abandoned child. With their pinched faces and thin limbs, the ragged street children found throughout Kinshasa, the Democratic Republic of Congo's fetid capital, are the bearers of wickedness and sin. Most have been cast out of their homes for being "witches" and, supposedly, bringing every kind of misfortune on their families. A visceral fear of "possessed" children is sweeping Congo's cities, causing tens of thousands of boys and girls to be...