When the paper trail runs out, Dr. Gates visits scientists who are using DNA analysis to trace ancestral roots. With DNA results and genealogical research in hand, Gates meets with leading historians of the slave trade, and along the way, he learns more about his own ancestry. Finally, Professor Gates and one guest journey to Africa, where they visit the port from which the participant's patrilineal ancestor was most likely shipped into slavery, and meet local tribal elders, who may be the participant's long-lost cousins.