That’s when the forest began.

They didn’t understand at first. They were both so accustomed to the sound of rain inside Corbenic – trickling through drainpipes; dripping steadily, rhythmically from leaks in the ceiling into half-filled buckets; pelting onto iron roofs.

But this – this was not inside rain. It was outside rain. It was the soft patter of spring rain on the hard ground of winter. The healing rain whose tiny fingers painted green over brown, on which the drooping heads of flowers supped, in which birds preened themselves. The rain that fell on new graves and brought the buds of grass out of the freshly turned earth.

And it was falling on their heads and bodies, washing the plaster away, drenching their hair and their clothes. It was soaking the carpet in the hallway beneath them and streaking down the walls around them.

It wasn’t long before they saw the first sproutings of life. First there was fungus – mushrooms and brightly coloured, uncanny-looking growths emerging quietly through the carpet, with a fresh, undeniably vegetative scent. Then there was grass, a fine shading of green at first, but it grew rapidly around them until they had to jump up out of its way, for it was pushing up uncomfortably beneath them, surprisingly powerful. Then there were the saplings, splitting the walls, their roots pushing under and then ripping open the carpet, the canopy of their leaves and branches destroying the ceiling and protecting them from the full force of the rain.

And then they were in a forest, and the remnants of the building had become rocks, and they were standing on a mountain path between the trees that seemed to be leading somewhere.

But the strangest thing of all was that the forest seemed so familiar. Deirdre stared around her. It was beautiful, it was the most beautiful thing she had ever seen, apart from the treasure she could not remember, but she knew the forest was somehow like the treasure, that they had the same origin, were part of the same entity.

When she recognised it, she did so not so much from the way it looked, as from the way it made her feel.

‘It’s you,’ she said suddenly. ‘The forest is you. We’re inside you.’

Gal just stared at her, his face still dusty with plaster and streaked with tears.

‘What?’

‘Don’t you recognise yourself?’ she asked him gently, loving his face, loving him.

‘I – I –’

The rain was easing now. They were both soaked to the skin and should have been cold and uncomfortable, but Deirdre felt happier and warmer and safer than she had ever felt in all the days of her strange existence. She knew that, all her life, she had somehow been dwelling inside her grandmother, imprisoned in her grandmother’s mind. Now she had entered the soul of Galahad.

The rain was Gal. The trees were Gal. The very air she breathed was Gal. His face, his warmth, his life were everywhere.

He seemed bewildered, but she took his hand and pulled him forward, along the path.

It was then that they caught sight of the little girl.

It wasn’t the second little girl, the terrifying one with the blonde bob and the uncanny abilities who was the ghost of Deirdre’s grandmother. It was the first one, the one in the white nightgown, with the long straight silvery fair hair, the one they had seen walking away from them when they first stepped out of the flat onto the landing, before they had got trapped in Deirdre’s grandmother’s memories. She was walking away from them again now, some distance ahead of them, along the path. She walked slowly, in a deliberate, absorbed, and yet somehow absent manner. She walked as if she was dreaming. She seemed about five years old.

They both knew they should follow her, but as they did so, a curious thing happened. The closer they came to her, the older she seemed to be.

She had been five or so when they first caught sight of her; before they had gone many steps she seemed seven or eight; then twelve; then fourteen.

And still she walked slowly away from them, and although they were walking as briskly as they could, and her pace never changed, it seemed difficult to catch up to her.

The path ahead of them became a rough stairway of rocks; slowly, gravely, dreamily, the girl began to climb it. The sun was shining through the heavy canopy of trees, dappling their vision, the window of sky directly above them was cobalt blue, and yet Deirdre knew they were still inside Corbenic; that it had somehow become Galahad’s domain, as if the seed of him had been planted in the very centre of it and suffused it with life, his life. They climbed the stairway behind the girl, who was now almost a woman, and it was difficult – steep and uneven and mossy and damp; but as they climbed, Deirdre’s joy grew and grew, for she already knew what the girl was leading them to; what they were about to find.

When the girl ahead of them reached the top of the stairs they saw her pause, as if waiting. They had almost caught up to her when she suddenly turned and looked at them calmly.

Deirdre froze on the stairway.

She was looking into a mirror. The girl’s face was her own. And at the moment she recognised her, the girl disappeared.

There was a small cave at the top of the rocky stairway; the entrance was barred by an iron gate; the cave was suffused with a gentle red-gold light; the sleepwalking girl of many ages with Deirdre’s face had led them to it.

Deirdre brushed away her confusion, dismissed her uneasiness. Surely, surely, their trials were over.

‘It’s here! It’s here!’ she cried. ‘We’ve found it!’

She was breathing hard with the effort but she dragged herself and Gal up the final steps and leant for a moment, all but exhausted, against the gate, before pressing down the latch and letting them in.

There was the room of glass. There was the iron plinth. There was the crystal box, from which shone the warm, red-gold light. And there, inside it, was the creature they had seen once before, all those years ago, and forgotten, the thing whose existence had haunted them ever since, the red-gold thing the size of a fist that moved constantly, rhythmically, as if clenching and releasing, clenching and releasing, like a little animal, like a ruby-coloured frog, like a sea anemone.

‘This was why I couldn’t leave!’ Deirdre whispered. ‘This was what I had to tend, and guard, in my sleep. This is what we found, when we were five . . . Do you remember? Do you remember?’

And she took up the box and cradled it against her breast. Then she gestured with her head for him to open it. Gal stared at her. Then, carefully, he lifted the lid.

They both looked down at it.

At first all they saw was its beauty. It was jewel-like – a living ruby, only soft – its movements both strong and fluid. Then it began to move more violently and rapidly, as if in response to being observed.

They both recognised it at the same moment. All at once, at last, they knew what it was. They couldn’t have known, at five. But they knew now. Confused, Gal lifted his hand as if to touch it, then let his hand drop.

And finally Deirdre understood.

She thought of her grandmother’s hatred of Gal, the grandson of her father’s mistress. She thought of her hatred of all men, because of that original man, her father, and his betrayal of her. She thought of her grandmother’s resentment of their friendship – hers and Gal’s – even when they were only five, and how she had hated Gal’s scepticism, his resistance to her power, his cool appraisals of her statements. She remembered the rabbit, its death and disfigurement.

She remembered her grandmother’s vow to take revenge – on Elaine, on men – for her mistreatment as a child.

She remembered the sheer intensity of her grandmother’s emotions – an intensity so concentrated, so obsessive, so fanatical that it seemed to make possible the impossible.

And she remembered an experience so terrible that she had forgotten it until this moment . . . even though she now knew that the ghost-child grandmother had shown it to them.

She remembered being in a dark room somewhere in the bowels of Corbenic with her grandmother, as Gal lay unconscious on some kind of stone slab.

She remembered a knife like a dagger with a strange design on its hilt.

She remembered a wounding, and a tearing, and a receiving into a crystal box, which she held, as a small girl, between her hands.

And she thought of all the years she had been sleepwalking – rising in the dead of night to visit the crystal room at the top of the stone stairs, to tend and to guard – and she thought of how she could not remember this practice, this obligation during the daytime, could not even find the room.

And she thought of the strange, rhythmic thudding sound one could hear throughout the building, sometimes soft and steady, sometimes louder, sometimes hectic with fear or passion.

‘It’s a heart,’ said Gal in wonder.

‘It’s your heart,’ said Deirdre.

For a moment Gal didn’t understand what she was saying to him. He gazed at her blankly. Then his face changed and he lurched forward and caught hold of the plinth. He leaned on it, gasping for breath.

Deirdre just hung on to the box. She could not afford to let it go. She watched him trying to regain his composure, trying not to collapse utterly with the sheer weight of the revelation. She knew what he was feeling. She knew how terrifying it must be, to see your own heart, disembodied, in a crystal box.

And she thought, my grandmother has won. She is God after all. She took Gal’s heart. She used me as a cat’s paw. Between us we have destroyed his life. And yet he lives. Who but an evil god could work such cruelty?

And now, she thought, because of her, I have lost Gal’s love, just when, at last, our love was fulfilled. This was her intention. This was her plan. Now he will hate me. For how could you love someone who helped your mortal enemy tear your heart out?

Her sense of doom – the sense of doom she had had all her life – had been justified, a thousand times over.

‘I was right,’ she murmured in sad wonder. ‘What I said to you that day was true. I am a witch. Like my grandmother. The kids at the high school – they weren’t wrong. I was a witch all along. I belonged at the stake. It’s like I told you, all those years ago. You shouldn’t have saved me, Gal. You should have let me burn.’

‘You’re not a witch,’ said Gal immediately, although he was still leaning, weak with shock, on the plinth. He said it as if he would have said it with his last breath.

Then he paused, trying to summon strength again.

He couldn’t think about it. He couldn’t think about it. He could not hold the thought in his head. This terrible knowledge – that he was not whole, that the most important part of him had been stolen, that violence that had been done to him – he could not bear the thought of it.

But he had to bear it.

He shut his eyes. He tried to find a way to live with this knowledge. But all he could do was float helplessly, as if there was no ground to stand on, nothing to hold on to.

So that was it. That was what she had done. That was her revenge. She had taken his heart.

And she had spent the rest of her life afraid – in mortal terror of the living heart she had buried at the very centre of Corbenic.

She had made the very building bigger and bigger, to bury it more deeply.

She had condemned him to a kind of life-in-death. And she had set Deirdre the impossible task of keeping his heart alive, outside his body, while he himself was banished, kept apart from his own heart and the person who tended it.

An impossible task. And yet Deirdre had achieved it.

In his head he heard the ghost-child grandmother during that last haunting, the strangest of all, the one he hadn’t understood, hadn’t even believed. You trust Deirdre, don’t you, Gal? You would trust her with your life? She had tried to get him to lift the sheet; she had tried to make him see himself, the sacrifice, on the cold slab. But most of all, she had been trying to destroy his love for Deirdre.

But she could never do that. Never.

He reached out towards her. He wanted to take her hand, to kiss it, to rub his cheek against it; he wanted to hold her, he wanted to bury himself in her; he wanted, he wanted.

Nothing mattered like Deirdre. Not even this. He could live knowing that his heart had been taken from his body. He could not live without his love for Deirdre.

‘It wasn’t your fault,’ he began again faintly.

Deirdre hung her head. She wished she could believe him.

‘Think, Deirdre,’ he urged, for it was desperately important to him that she understood. ‘She took the heart – but what did you do?’

Deirdre stared at him mutely, abject, like one condemned.

‘Deirdre, what were you doing all those nights, visiting my heart in your sleep?’

Deirdre cradled the crystal box against her breast. Her eyes filled with tears. Finally, tentatively, she whispered, ‘I was looking after it.’

‘You were keeping it alive! You couldn’t have stopped her taking it. You were only five. You didn’t understand – how could you? And she had such power – over you, even over me. Her will was so strong, she could make me leave you. She could make me do the thing that I least wanted to do in all the world.

‘You’re not a witch – or not the kind your grandmother is. Because, Deirdre, there are two kinds of witches.’

Deirdre looked startled.

‘Two kinds?’ she whispered.

Gal seemed to be gaining strength. He pushed himself upwards with the heels of his hands.

‘There’s the kind your grandmother is,’ he said. ‘And then there’s your kind. You’re a white witch. A healer. You have power too. But it’s all in your love. Don’t you see?’ He took a deep, rasping breath, and then another. ‘She used you, to keep the heart alive. She couldn’t have done it by herself. But she lied to you. And she crushed your vocation. Or – bent it to her needs.’

Deirdre stared at him sadly.

‘I was a healer,’ she repeated, remembering that she was dead, and that it was all too late.

It was so plain to her now – how wrong she had been to obey her grandmother unconditionally, to let the old woman live through her. She had been given her own life, her own vocation, her own beliefs, and yet she had handed them over to her grandmother to dispose of. She thought about all the ways in which she had privately disagreed with her grandmother, thought her judgements harsh, unreasonable, and yet had shut her mouth and acquiesced. Even when her heart almost broke.

And she thought of how, by choosing not to go with Gal on that last occasion, she had in effect chosen death.

‘A healer,’ she whispered again.

And she looked down at the heart in her hands.

Suddenly she knew what she had to do.

‘Gal,’ she said. ‘Listen to me. I’m dead – my life is over – but I’m haunting Corbenic because I can’t leave your heart, because I’m guarding your heart. You’re alive – but you’re haunting Corbenic too, because your heart has been stolen from you, because your heart is imprisoned here. While ever your heart is in this box in the centre of Corbenic, neither of us will be free.

‘It’s like you said, Gal. I was meant to be a healer. And I still can be. Don’t you see? I have to undo the evil my grandmother did. I have to disobey her. I have to act on my own free will. As if I am my own person, and not her slave. I have to give you your heart back.

‘Then you can live – and I can die.’

For a moment there was silence. Gal was so dismayed he could hardly move, hardly talk, but he shook his head faintly and whispered, ‘No!’

All he could think, all he could feel was that he was about to lose her again. It was too cruel. He couldn’t bear it. He slid to his knees, still holding onto the plinth, and said, holding his arms out to her, ‘Don’t die again.’

And he was a child again – five years old – but even as a child his face had never looked so vulnerable.

Deirdre knelt and put the box on the ground. Then she crawled over to where he sat on the ground, put her arms around him and cradled him against her.

‘Don’t choose death.’

‘But I can’t do it,’ he said. ‘I can’t go on living without you. All the years, Deirdre, all the years in front of me, and all without you . . .’

‘I’m a ghost, Gal. But you belong to life. You have to live.’

He shook his head.

‘Not if you destroy the heart.’

He had pulled away and was looking at her steadily. She had never seen him look so serious.

He made a sudden movement towards the crystal box. Instinctively, she placed herself in front of it.

‘Please, Deirdre. Destroy the heart. I don’t want it back. I don’t want to go back to life. I want to come with you.’

Destroy the heart.

Deirdre gazed at him. The tears filled her eyes, again and again, fell steadily down her cheeks. She stroked his hair, kissed his forehead, his nose, his chin, his mouth, and all the while he pleaded with his eyes.

Her heart was breaking.

She had always been so timid, so obedient, so afraid of her grandmother, so easy to manipulate. But there was one thing she knew she would never have done, on pain of death, even if her grandmother had told her to, even if Gal had asked her.

‘I will never destroy your heart, Gal,’ she said. ‘I would keep it alive even if I had to feed it with my own.’

And Gal looked at her as if his last hope had died.

‘Oh, Gal,’ she said, ‘it was Grandmother who always said No. You always said Yes.’

Gal clung to her.

At first he thought he could not do it – that he simply could not face life without her. Everything within him rebelled. It was true, all he wanted to say was no, no, no – just like Mrs Dark.

But deep inside he knew he was beaten. He knew she would never destroy his heart. And he knew he could never choose death over life, no matter how lonely that life would be.

‘Lie down,’ she said. ‘Give me your jacket. I’ll put it under your head.’

He stared at her with such love she almost wavered in her resolve. And she thought, surely I am mistaken. He doesn’t want to let me go but he can’t love me, not really, not after all that’s happened.

‘Lie down,’ she said again softly.

She couldn’t help him; she was holding the heart in both her hands. But using the plinth as support, he let himself down onto the mossy floor of the cave, gazing at her all the while.

‘I love you,’ he said.

She stared at him, astonished.

‘You love me?’ she repeated. ‘Still? Knowing all this? Gal, how could you?’

‘Because I do. Of course. No matter what. Forever. That’s what love is, Deirdre. Even if it had been your fault, I would still love you.’

Deirdre shut her eyes.

‘You love me,’ she said. ‘Still. Despite everything.’

She thought for a moment – she thought about the entirety of her life. Then she whispered, ‘I was loved. No matter what. I loved, and I was loved! Oh, Gal, how could anyone ask any more? I love you too. Forever. Nothing I could give you would be enough. But I can give you back what is yours.’

And she knelt and placed the crystal box on the moss beside her. Then she leant over, kissed his lips one last time, parted his shirt, and began to kiss the wound in his chest. She felt a burning from it on her lips, as if she were drawing the pain out into herself. And the wound parted, as she knew it would – but not violently; it was if it opened to her, like the door to the most sacred of caves.

He was gazing up at her with the most profound expression of trust in his eyes. He was like a five year old, then a man.

And she took the heart from the crystal box into her white hands and felt it beating between them, soft and power­ful – for the heart is a muscle that grows strong with use, and Gal’s heart had been used and used and used.

She brought it up to her lips and kissed it, that pure heart. Then she reached in and replaced it in the cavity of his chest. And kissed the wound, again and again, kissing it shut.

His eyes were growing heavy. She gazed into his face and stroked his hair back from his forehead.

‘You will be released now,’ he murmured. ‘There will be nothing to bind you to earth.’

‘You will be free too,’ she said. ‘Free to live. Go to sleep. I’ll stay with you.’ And as he lost consciousness, she said, ‘Sleep, Galahad. Then wake, and live.’