Books: Guilt around the picture-frame: A Harlot's Progress by David Dabydeen Jonathan Cape, pounds 10, 281pp

Hilary Mantel admires the surprising story that emerges from the shadows of slavery

PLATE TWO of Hogarth's series A Harlot's Progress finds Molly Hackabout in mid-career; no longer the fresh country girl with a rose in her bosom but the mistress of a rich Jew. In the background, a young lover sneaks from the room; a pet monkey plays on the floor; a little black boy carries hot water to the tea-table. In Plate Three, Moll will be taken up by Justice Gonson. Four finds her in Bridewell, Five a dying woman shrounded in blankets; Plate Six, in her coffin.

As prints, pirated, the images sold in their thousands. Composed with the formality of religious art, they were still democratic. They mirrored the people of England to themselves, titillating them, encouraging them to moralise. They allowed the common man to chortle at the hypocrisy of his betters, to be shocked by his own collaboration in vice: to hiss at the Jew, and shed a sentimental tear over the monkey and the slave.

It is the black boy in the turban whom David Dabydeen has freed into his text. He has various names: Mungo, Noah, Perseus. He also has an unknown, original name, which he has forgotten, just as he has forgotten, or has never known, the name of the African village from which he is captured.

On board ship, Captain Thistlewood sodomises him and makes him a Christian. From now on he must not only suffer, but try to make sense of suffering and see it as the road to salvation. Captain Thistlewood will put a brand on his forehead; the pain will erase his memories of Africa. In future - for the process of colonialisation is a thorough one - he will derive knowledge of his own nature through travellers' tales written by Englishmen.

When Mungo becomes an old man, another Englishman is waiting to write about him: Mr Pringle, the abolitionist. "Something must be said - there must be a story," Mr Pringle urges. Mungo knows that it is as much for the sake of the slavers as for the slaves themselves that abolition is desired, since slavery blights the moral economy of the nation. He is required to tell the story Pringle wishes to hear, a trite if bloody tale, "a story of pimps, whores and screaming nigger boys". But he cannot collude, because a chorus of voices of dead villagers has followed him through his life, with "their expecations of alternative lives, lives which they did not live but which were possible".

So the narrative fractures. Mungo/Noah/Perseus is at once the dispossessed African and the inheritor of classical wisdom from a tribe of "lost Alexandrians"; the brand on his forehead is the symbol . A woman called Betty fattens him for sale; from her he learns of Mary, the country girl whom she nurtures/ betrays/ rescues. Betty herself may be Moll Hackabout. Christ may be redeemer and executioner. "I had many beginnings," Mungo says, and he has many middles and ends.

We exist as fragments of each other's stories, Dabydeen suggests, in a series of infinitely negotiable contexts, inside a history which is in itself mutable. But if Mungo, that "ruined archive", is fit to tell the tale, are we fit to hear it?. Waiting for Mungo to deliver the raw material for a tract, Mr Pringle doodles "a series of ears drooping and mutilated."

We are condemned as voyeurs, and we hope that after condemnation will come a sentence, one that will lead us, not simply to contemplate the elevation of guilt into liberal ideology, but to the knowledge of what happens next. But there is no "next"; there is only "different". History cannot be re-experienced, only re-created, and before the immensity of the imagination's task, "English itself falters".

This is an intellectually fastidious book, honest but never plain. Because of the terms it has set itself, it loses energy after its brilliant opening pages. Yet Dabydeen's prose is terse, vigorous and constantly surprising. Like Mungo, he shatters expectation. His strong vision allows for little negotiation with the reader. It suggests that, for the recreation of lost meaning, it is necessary to strike off the fetters of narrative, and be released into poetry.

Hilary Mantel's latest novel is `The Giant, O'Brien'