In the spring of 1703, a young African boy stepped off a slave ship in Constantinople, the gateway between East and West. Huddling in chains, with other frightened captives, the seven-year-old claimed to be a prince of Abyssinia, a "noble Moor" kidnapped and stolen out of Africa. His tragedy was shared by millions of black people caught up in the Islamic slave trade, but his destiny was unique: rescued by Peter the Great, the young African became...