Captains of the sands"" are those African overseers who sold their own people into 18th-century slavery--and the narrator of this gritty, dark picaresque adventure soon finds himself among them. He is English Tom Derker, who's orphaned when his farmer-parents die during the horrific snowbound winter of 1749. So, eagerly falling in with his charismatic Uncle William, a slaver sea-captain, Tom soon finds himself sailing the Liverpool/West Africa/West Indies trade triangle--featuring a grim, pathetic form of slave-trade on the Ivory Coast (bartering for one or two at a time, with many dying before Uncle William gets a full cargo). Then William and Tom are taken captive, lodging with the kind Jola tribe until they are ransomed: Tom falls in love with young native girl Fourfarthings before he sets sail again. And when, months later, a group of Jolas is sold to William, Fourfarthings is among them. So Tom's attitude towards the slave-trade begins changing--especially when a beloved alcoholic officer is shot while attempting (sober at last) to free the slaves. And he buys Fourfarthings at a ""scramble"" (buyers chase and tag the desired slaves) in the Indies. But Tom's dream of their life together in England is dashed when Uncle William takes Fourfarthings as his own willing mistress and informs Tom of his true parentage: Tom deserts, becomes pot-boy in a whorehouse, joins the decadent Antigua high-life, eventually kills William (now shipless and alcoholic), and takes off to try (profitably) his fortune in the American colonies. Finally, then, back in England, active in the Anti-Slavery Society but still involved (second-hand) in commercially profitable injustices, Tom assesses his seven years in the slave trade and admits never having had ""one true and equal relationship with a black person, man or woman, and now it was too late, because I knew too much, and they would always shut me out."" A bit preachy, perhaps, in its moral lessons--but a taut, dramatic adventure that reworks the old picaresque conventions with a strong, grimy sense of raw atmosphere and ugly realities.