Behind the colour bar

There's a telling scene in Claire Robertson's astounding debut novel in which two men sit on the veranda of a farmhouse in the interior of the Cape Colony one afternoon in 1794 and banter about "the cult of sub-classification".

This, after all, is the age of enlightenment and one of the men, Calcoen, the farm master, is taken with this business of the calliper and the tape. He has, for example, the measure of his guest, French wigmaker Le Voir: Homo sapiens Europaeus, "active, very clever", "ruled by laws".

The calibrations of Le Voir's apprentice, freed slave Katrijn van der Caab, are, however, not as encouraging. Her type are "melancholy and greedy", "severe, haughty, desirous" and "ruled by opinion". And, at "the dull end of the sorting system", there are those like the slave Melt, with whom Katrijn falls in love, who are "black, impassive, lazy", "crafty, slow, foolish", and "ruled by caprice".

For her part, Katrijn, the protagonist in one of The Spiral House's two narratives, has the measure of this pseudo-science.

"Though it was foolish stuff," she reveals, "I could not smile at it ..."

Neither does Le Voir approve, and he gently mocks Calcoen about his pursuits: "And as for the cataloguing of the women of this place from best beddable to worst according to their origin ..."

This subversion, if I may, of the obsessions of eugenics, was to Katrijn "the worse and the funnier because in the list the pink and white homeland ladies were little prized for tumbling, and the mere Malagasy girls so keenly sought after for the sport".

Such a categorisation was indeed once familiar with Cape gentry, and it was noted in the journals of Anders Sparrman, the Swedish naturalist and abolitionist who explored the Cape extensively in the 1770s. His work, and his spirit of inquiry, is very much present in Katrijn's story, which begins as a mission with Le Voir to travel from Cape Town to the remote farm Vogelzang, where a young mistress who has lost her hair through disease is in need of their services.

As daily life unfolds, Katrijn slowly learns of the farm's dark secret and the strange house that Calcoen is building at a site hidden from the homestead and outbuildings. As she notes ominously: "Something is wrong, but no one will say what."

The Spiral House's second narrative takes place in 1961 in a rural community in what was then the far northern Transvaal on the eve of the country launching itself as an Afrikaner republic.

It's the story of Sister Vergilius, a young nun at a mission hospital who yearns to break free of her order and how she, too, comes to find love after catching the eye of bachelor farmer Francis Shone, the district's "only known communist", as the arrival of a group of American pensioners travelling from the Cape to Cairo in a convoy of Airstream caravans brings an unsettling excitement to the community.

It is through Francis that the link with Katrijn's narrative is first revealed - in the pages of a historical journal, possibly a reprint of Sparrman's travelogues, which he reads at night on the veranda of his own farm.

As Robertson puts it in a stunning example of her craft: "Here, where history is either fable or tribal anthropology or a cold wall of begats, he will ignore these attempts to borrow the credentials of the forebears; he will read her tale as that of a girl he must know. He thinks: I side with her, but how can she love me in return, and knows he is no longer thinking of the freed slave, or not only of her."

It is the Vergilius and Francis narrative that is, perhaps, the more familiar; its concerns, after all, are of the more recent past. Here, again, are the tropes of the apartheid era - security policemen and banning orders, the instruments employed by a state that has, in the words of one critic, "declared war on its citizens".

But it is Katrijn's story that is the more revelatory, and the one I believe will earn this novel the accolades it justly deserves. Here the first-person narrative is rendered, painstakingly, in the prose style of the late 18th century. It is archaic, but not laboured, and gives the book much of its music and magic.

It is a powerful, often darkly comic and richly rewarding work.

A disclosure of sorts. I've known Robertson, a copy editor at the Sunday Times, for some 20 years. She is a friend. But then, I have lots of friends, an increasing number of whom are novelists.

'The Spiral House' is published by Umuzi. At Exclusive Books for R206