‘Why are you doing this?’ I asked her.

She took the Knife of Laufrodedd from the tortured clay skull. ‘Let her sleep,’ she crooned, ‘or maybe not?’ And with that she gave a mad laugh and snatched an iron ladle from the Basket of Garanhir, scooped some burning embers from the smoky fire and scattered the burning scraps over the body and I imagined Ceinwyn shuddering and screaming, her back arching with the sudden pain, and Nimue laughed to see my impotent rage. ‘Why am I doing it?’ she asked. ‘Because you stopped me from killing Gwydre. And because you can bring the Gods to earth. That is why.’

I stared at her. ‘You’re mad too,’ I said softly.

‘What do you know of madness?’ Nimue spat at me. ‘You and your little mind, your pathetic little mind. You can judge me? Oh, pain!’ And she stabbed the knife into the clay breasts. ‘Pain! Pain!’ The mad things behind me joined in her cry. ‘Pain! Pain!’ they exulted, some clapping their hands and others laughing with delight.

‘Stop!’ I shouted.

Nimue crouched over the tortured figure, her knife poised. ‘Do you want her back, Derfel?’

‘Yes,’ I was close to tears.

‘She is most precious to you?’

‘You know she is.’

‘You would rather lie with that,’ Nimue gestured at the grotesque clay figure, ‘than with Olwen?’

‘I lie with no woman but Ceinwyn,’ I said.

‘Then I will give her back to you,’ Nimue said, and she tenderly stroked the clay figure’s forehead. ‘I will restore your Ceinwyn to you,’ Nimue promised, ‘but first you must give me what is most precious to me. That is my price.’

‘And what is most precious to you?’ I asked, knowing the answer before she gave it to me.

‘You must bring me Excalibur, Derfel,’ Nimue said, ‘and you must bring me Gwydre.’

‘Why Gwydre?’ I demanded. ‘He’s not a ruler’s son.’

‘Because he was promised to the Gods, and the Gods demand what was promised to them. You must bring him to me before the next moon is full. You will take Gwydre and the sword to where the waters meet beneath Nant Dduu. You know the place?’

‘I know it,’ I said grimly.

‘And if you do not bring them, Derfel, then I swear to you that Ceinwyn’s sufferings will increase. I shall plant worms in her belly, I shall turn her eyes to liquid, I shall make her skin peel and her flesh rot on her crumbling bones, and though she will beg for death I will not send it, but only give her pain instead. Nothing but pain.’ I wanted to step forward and kill Nimue there and then. She had been a friend and even, once, a lover, but now she had gone so far from me into a world where the spirits were real and the real were playthings. ‘Bring me Gwydre and bring me Excalibur,’ Nimue went on, her one eye glittering in the cave’s gloom, ‘and I shall free Ceinwyn of her Otherbody and you of your oath to me, and I shall give you two things.’ She reached behind her and pulled out a cloth. She shook it open and I saw it was the old cloak that had been stolen from me in Isca. She fumbled in the cloak, found something, and held it up between a finger and thumb and I saw she was holding the little missing agate from Ceinwyn’s ring. ‘A sword and a sacrifice,’ she said, ‘for a cloak and a stone. Will you do that, Derfel?’ she asked.