The next day the sorceress came to visit the king again. She had burned three more books the night before, she said, and now offered him the remaining three, for the same price she had originally asked for all nine. Though it vexed him greatly, Tarquinius paid the woman the sum she demanded.

And so, because Tarquinius hesitated, the Sibylline Books were received in only fragmentary fashion. The future of Rome could be discerned only imperfectly, and the reading of auspices and auguries was not always precise. Tarquinius was both revered for obtaining the sacred texts and derided for not acquiring them all. The Sibyl of Cumae gained a legendary reputation for her wisdom. She was respected both as a great sorceress and a shrewd bargainer, having obtained the price of nine books for only three.

The Sibylline Books became objects of awesome veneration. They outlasted the kings of Rome and became the most sacred property of the Roman people. The Senate decreed that they should be kept in a stone chest deep underground in the temple of Jupiter on the Capitoline Hill, above the Forum. The books were consulted in times of great calamities or when inexplicable omens appeared. Those priests who were specially charged to study the books were constrained under penalty of death to keep their contents secret, even from the Senate. One curious fact about the verses became commonly known, however. They were written in acrostic; together, the initial letters of each line spelled out the subject of each verse. Such cleverness as would have driven a mortal to distraction must have been child's play for the divine will.

Because the books remained so mysterious, very few persons know exactly what was lost when, ten years ago in the final convulsions of the civil wars, a great fire swept the Capitoline and consumed the Temple of Jupiter, penetrating the stone chest and reducing the Sibylline Books to ash. Sulla blamed his enemies for the fire, his enemies blamed Sulla; in any case it was not an auspicious beginning for the dictator's three-year reign. Without the Sibylline Books to foretell it, did Rome have a future? The Senate sent special envoys all over Greece and Asia to search for sacred texts to replace the lost Sibylline Books. Officially, this has been done to the full satisfaction of the priesthood and the Senate. For those respectful of divine will, but sceptical of human institutions, the opportunities for fraud and bamboozlement offered by such a scavenger hunt are too staggering to contemplate.

It is no small indication of the depths to which the Sibyl of Cumae has fallen in public esteem, at least in Rome, that no envoy was sent to her when the original books were lost. Surely it would make sense to go back to the source in order to replace the arcane books – or did the Senate balk at the prospect of losing face in a second bargain with the Sibyl of Cumae?

Around the Cup, the Sibyl is still venerated, especially by denizens of the old Greek towns, where the chlamys is worn instead of the toga and Greek is spoken more often than Latin, not only in the markets but in the temples and law courts as well. The Sibyl is an oracle in the Eastern sense; she, or more precisely it, is a mediating force between the human and divine, able to touch both worlds. When the Sibyl enters one of her priestesses, that priestess is able to speak with the voice of Apollo himself. Such oracles have existed since the dawn of time, from Persia to Greece and in the far-flung Greek colonies of old, like Cumae, but they have never been wholly embraced by the Romans, who prefer that inspired individuals should interpret the will of the gods by watching puffs of smoke or rattling beans in a gourd rather than uttering the divine message directly. The Sibyl of Cumae is still venerated by the local villagers, who bring her gifts of livestock and coins, but she is not favoured by the fashionable elite of Rome who inhabit the great seaside villas; they prefer to seek wisdom from visiting philosophers and to bestow their patronage on the respectable temples of Jupiter and Fortune in the forums of Puteoli, Neapolis, and Pompeii.

I was not surprised to find the temple of Apollo attached to the Sibyl's shrine to be in a state of some decay. It had never been a grandiose structure, notwithstanding tales of Daedalus and his golden embellishments. It was not even built of stone but of wood, with a bronze statue of Apollo upon a marble pedestal at the centre. Painted columns of red, green, and saffron were surmounted by a circular roof, the underside of which was segmented into triangles and painted with images of Apollo overseeing various acts in the tale of Theseus: the lusting of Pasiphae for a bull and the birth of the Minotaur of Crete; the casting of lots for the yearly sacrifice of seven Athenian sons to the beast; the construction of the great maze by Daedalus; the sorrow of Ariadne; the slaying of the monster by Theseus; the winged flight of Daedalus and his doomed son Icarus. Some of the paintings looked very old and were so faded that they could hardly be discerned; others had been recendy repainted and glowed with vivid colour. A restoration was in progress, and I suspected that I knew the woman responsible.

The temple was situated in a nook of land hemmed in on three sides by walls of jagged stone. It was the only flat surface on the steep hillside, which otherwise was strewn with boulders; the great stones seemed to have frozen in mid-avalanche and were overgrown with twisted trees that looked as if their nailing limbs were outstretched to save themselves from falling. The priestess walked ahead of us with a serene and unfailing sense of balance, never setting a foot wrong, while Eco and I followed, slipping and sliding after her, sending bits of gravel flying down the hill as we grabbed branches for support.

The spot was secluded from sight and protected from the wind. A quiet hush reigned over us. Above our heads the fog struggled to push itself over the hilltop and emerged in tatters, casting the place into a weird, dappled mixture of darkness and sunlight.

Within the temple the priestess turned to face us. Beneath her hood her features remained hidden in darkness. Her voice emerged as strange as before, the way that Aesop says that animals would speak if they could, forcing their inhuman throats to make human noises. 'Obviously,' she said, 'you didn't bring a cow.'

'No.'

'Nor a goat.' 'No.'

'Only your horses, which are not a suitable sacrifice to the god. You have money, then, to purchase a beast for sacrifice?' 'Yes.'

She named a sum that did not seem outrageous; the Sibyl of Cumae was apparently not the hard bargainer she once had been. I pulled the money from my purse and wondered if Crassus would accept the expense as an addendum to my fee.

I saw her right hand for just an instant as she accepted the coins from me. It was an old woman's hand, as I would have expected, with prominent bones and patches of discoloured flesh. No rings adorned her fingers, and there was no bracelet on her wrist. There was, however, a smudge of blue-green paint on her thumb, just such a hue as Iaia might have been using that morning to touch up a bit of her mosaic.

Perhaps she saw the smudge of paint herself. Either that or she was eager for the money, for she clutched the coins and snatched her hand away, hiding it again within the sleeves of her robe. I noticed also that the hems of her sleeves were a darker red than the rest of her garment, stained by blood.

'Damon!' she called. 'Fetch a lamb!'

From nowhere a child appeared, a little boy who thrust his head from between two columns and then as quickly vanished. A few moments later he reappeared carrying a bleating lamb over his shoulders. The beast was not farm stock, but a pampered temple animal fattened for ritual sacrifice, kept clean and carefully groomed and brushed. The boy swung it over his shoulders onto a short altar before the statue of Apollo. The creature bleated at the touch of cold marble, but the boy managed to calm it with soft strokes and whispers in its ear even as he deftly trussed its legs.