The writer Caryl Phillips uses startling new evidence from a huge slave burial site discovered in New York City to expose the extent of slavery in both the northern and southern parts of the United States. The human remains discovered during routine building work in Manhattan smash the idea of slavery as a largely "Southern" phenomenon. The programme also draws on oral archive of the last people to be born into slavery in the American South and contrasts their experiences with surprising new detail about the lives of their northern counterparts.