'What happened to the nurse?'

'She was sent away. Or so I was told – I never saw her again. But I still remember those eyes of hers and her mouth moving.' She shook her head and her face relaxed a little from its former fixity of expression. 'We are all the victims of stories in one way or another,' she said, 'even if we are not in them, even if we are not born yet. I wasn't born then, but Thyestes cursed me too.'

'There might be curses we don't know about,' Sisipyla said. 'Then things would happen, terrible things, and we wouldn't even know why.' As always, it was the unexpected that troubled her imagination most, the monster in the dark cave, waiting to pounce on the unwary traveller. If you knew about the curse, at least you could be on your guard. For some moments it had seemed to her that she shared the memory of the cruel nurse's face, but of course that was impossible. Just a memory of unkindness, she thought. Any face would do for that. She had not expected much from the story of the double curse, being already quite familiar with it; but then this new story of the nurse and the nightmares had sprung out from inside the old one. 'Princess, we must prepare for the sacrifice,' she said. 'They will be waiting below.'

'Yes, it is time.' Iphigeneia made no move for the moment, however, but remained standing where she was, in the middle of the room. 'The same things happen over and over,' she said. 'Did you notice? The story goes off in all directions, but it is always the same story. There is the trick and the shedding of blood and the outrage to Zeus the Guardian, protector of guests and hosts. Atreus is dead, but my father is alive, the curse is on him too. But I can save him.' Her voice had slowed and deepened a little and her eyes were shining. 'By marrying Achilles, I can save my father, I can lift this curse from the whole family. Achilles is a great hero, there is no darkness on his name, he is under the special protection of his goddess mother, Thetis, and so of Zeus – it's no secret that Zeus has always had a soft spot for her. Even if Achilles is killed in the war and I am left a widow, it won't make that much difference, he can still use his influence from the Isles of the Blessed, he is certain to go there, being so well-connected, you know, and they keep their bodily forms and all their faculties there, not like those poor shadows in Hades. I went to the shrine of Artemis this morning to make a votive offering and I just stood on my own there and I felt she was in favour and understood my reasons.'

Devotion can still include irony towards its object, and it did not escape Sisipyla that her loved mistress talked as if she had had the luxury of a yes or no, whereas, given the wishes of her parents, it could only have been a choice between accepting gladly or reluctantly. As they went together into the short passage that led to the vestibule where their ceremonial clothes were kept, Sisipyla wondered if wanting to do what you in any case had to do was a sort of choice. No one would ever wonder about her in that way; no one would ever care whether she did things willingly or not, so long as nothing showed on her face. How marvellous and strange to be part of a family, even one with a curse on it, to have a father to save, to feel directed by the gods.

The white sacrificial robes, freshly laundered and scented with coriander seeds for purification, had already been laid out by Sisipyla. She helped her mistress to dress in the long-skirted, gold-trimmed gown, then the girdle of virginity, then the bib and apron of thick felt, tied at the back, covering the front of the body from the neck to the knees and marked here and there with the bloodstains that made the garments always more sacred. Clytemnestra, when handing over the duties of priestess to her daughter, had offered the services of her own women, who had been attending her for years and knew the procedures; but Iphigeneia had wanted Sisipyla and no one else for her dresser.

The dressing done, Sisipyla applied to her mistress's face the white chalk paste, silky and lustrous in appearance, which she had mixed herself in a shallow bowl, smoothing the paste with her fingertips, following the lines of the brows and nose and cheeks, making a perfect oval. No one could easily have recognized Iphigeneia now. It was a gleaming mask that looked back at Sisipyla, not a human face at all, only the colour of the lips and the dark pools of the eyes breaking that stiff composure. Sisipyla rubbed her fingers clean with a cloth, then went to the paint pot and brush standing on the low stone table. The moon-mask was dry already; with the thin brush she made tiny vermilion circles on Iphigeneia's cheeks and chin and forehead, four in number, in token of the blood that was to be offered, and the phases of the moon.

When this was done, Sisipyla dressed hastily in her plain white gown, and they were ready. They passed from the vestibule into the corridor that led to the staircase on the south side of the palace, Iphigeneia walking in front, Sisipyla a step or two behind. The last part of the corridor, before the head of the stairs was reached, was a roofed terrace, open on one side. Beyond the stone columns that held up the roof, the perfect disc of the moon was rising, intensely bright but clear and definite at the edges, as though pasted on the night sky.

'Walk beside me till we are outside,' Iphigeneia said, speaking over her shoulder. The voice was unrecognizable, without inflections, coming in a single tone because of the stiffening of the paste round her mouth. She had never asked this before, and Sisipyla, obeying, knew it was because they would never again make the sacrifice together in quite the same way. Nothing would be the same, even if they did the same things. At the next full moon, Iphigeneia would have laid aside the girdle, she would wear the tiara, she would be different. Sisipyla felt again the breath of change, the chill of loss. As they walked together side by side, stepping through the bars of moonlight cast over the pavement between the columns, Iphigeneia took her hand, they walked hand in hand together to the head of the stairs, and in Sisipyla's joy at this there was also the knowledge of loss.

In the cobbled yard below the steps the people of the procession were waiting, the gilded, beribboned goat in their midst, held by two men with leashes of corded silk. Moonlight lay on the upper wall of the terrace but the yard was still in shadow and the attendants had lit torches while waiting. All bowed low to the ground as Iphigeneia descended, but when they straightened up again Sisipyla gave them a sharp looking-over. The only ones that should be there, at least to start with, were the people who looked after the shrine and those who had a part to play in the sacrifice; too many people who you never saw at other times tried to get in on the sacrificial procession for the sake of the roasted meat afterwards. Others would tag on while the procession was on the move, but that was different, more acceptable to the goddess – they weren't barefaced enough to pretend they had some official status.

Iphigeneia walked forward, leading again now, making no acknowledgement of the people waiting. Sisispyla was handed the sacrificial basket, which she had prepared herself, with the knife concealed beneath the grains of barley. She placed the basket on her head, with her left arm upraised to support it. The torch-bearers fell in on either side and the procession began to follow Iphigeneia across the yard and through an archway into the wider open area, unpaved and uneven and without enclosing walls, where the altar stood.

Here in the open they were in the full flood of the moonlight. The torches were extinguished and after this silencing of the flames there was at first only the scrape of their steps on the rough ground. Then came the wavering music of the flutes, eclipsing other sounds. Sisipyla was grateful that the goat remained silent. She had, as usual, mixed the dried juice of the poppy fruit into the mash of its last meal. This was a matter of careful judgement: too much, and the beast would stagger; too little, and there was the chance, when it came into this open space, that it would forget it was a captive, get a whiff of some exciting possibility in the night air or the stirred dust under its hoofs, and utter some sound of complaint or belligerence that would sully the sacrifice and be taken as a bad omen. And this, since she had chosen and prepared the animal, would reflect on her.