‘All right, listen up, crew!’ Polly’s father says, floating to the top of the chamber so that all the ghosts can see him. ‘I have great news. My brave Polly has come all this way – with her equally brave friend,’ he adds, nodding towards Buster, who gives a shy little wave, ‘to do the spell to put the gorvan back to sleep.’

The ghosts all look at each other, their eyes widening in surprise. Then they cheer wildly. They float around the cavern, slapping each other on the back and hugging each other, tears springing into their shimmery ghostly eyes. ‘Oh, thank you, Polly!’ they call. ‘Thank you! Thank you!’

‘Five long years,’ one ghost says happily. ‘Five long years and finally we can move on.’

Polly frowns. She looks at her father. ‘Move on?’

‘Yes, Polly,’ he says. ‘I vowed to stay here to guard the mines, to make sure the gorvan never escaped, and my faithful mining crew refused to leave my side. For five years we have haunted these mines to make sure no witch, warlock or monster ever came in here. Once you have done the spell to put the gorvan back to sleep, we will no longer be needed. We will be set free.’

Polly feels her heart begin to curl up a little inside her chest. She is not sure this is what she agreed to. ‘You mean, if I put the gorvan back to sleep, you are going to go away? Again?’

‘Oh, Polly,’ her father says, understanding what Polly is saying. He takes her to one side, where the ghosts can no longer hear their conversation. ‘These ghosts have waited five years for this moment, Polly. Imagine. Five long years neither here nor there. It is time, now, for us to move on.’

‘No!’ she says. ‘You can’t!’ Fresh tears push up through her chest. ‘I’ll come and visit you,’ she sobs. ‘I’ll come every day!’

‘Polly,’ her father says, his eyes shining with tears. ‘You have school and your friends and your future. It would not be a life, visiting the ghost of your father in a dark, dangerous mine each day. You would become a ghost yourself. And think of all these other poor souls. This is not just about you and me, my heartkin. You know you must do the spell. Put the gorvan to sleep and save Blackmoon Coven before it’s too late. And then never come back here again.’

Polly looks around at all the other ghosts filling the cavern, watching her with hopeful eyes. She knows her father is right. She can’t imagine what it has been like for them all this time, waiting for someone to come and release them. She takes another deep breath.

‘All right,’ she says quietly. ‘What do I need to do?’

‘Thank you, Polly,’ he says. Then he turns back to his ghostly mining crew. ‘OK. All of you stand back. Polly is going to do the spell.’

‘Woohoo!’ call some of the monsters, and two of them do a happy jig.

Buster looks at Polly and gives her the thumbs up. ‘Go, Polly!’ he whispers. He smiles at her proudly. Of all the happy, dancing creatures in this deep, dark, gloomy chamber, Buster is the only one who understands how much Polly has missed her father since he’s been gone – and how much she has dreamed of seeing him again. He is the only one who truly understands the sacrifice Polly is making by letting him go.

Polly’s father turns to her. ‘You have the stones, don’t you?’

Polly nods, wiping her eyes. She holds up the little pouch, damp from the heat of her palm.

‘These stones, Polly, come from the very deepest darkest parts of this mine, from right above the gorvan’s heart. That is why they are so powerful,’ her father explains. ‘The stones will make sure the spell does what it’s supposed to do. Once you’ve used them here you can take them home with you again, but make sure you keep them somewhere safe. Never let them fall into the hands of someone else. For while they can be used to put the gorvan to sleep, they can also be used to wake it again.’

Polly looks down at the little silk pouch in her hand. She has had the stones for as long as she can remember. She knew they were precious, even before Miss Spinnaker activated them, but she would never have dreamed they came from right above a gorvan’s heart. Polly promises her father she will guard them with her life and he smiles at her proudly.

‘So, what’s the spell?’ she asks nervously.

Her father smiles. ‘You know it already, my lovely. I’ve been teaching it to you your whole life.’

‘You have?’ Polly frowns, confused. ‘I … I don’t know what you mean.’

Her father beckons Polly over towards the eerie purple wall. As they approach, she realises that the strange purple light is in fact a fine mist, oozing through the rocks into the chamber.

‘The spell is written here,’ her father says.

She looks where he is pointing and steps in closer, worried that she won’t be able to read it properly. Her father doesn’t know how the letters dance around in Polly’s mind, and she feels a flutter of panic.

What if I mess this up? she worries. What if I read out the spell wrong and instead of putting the gorvan to sleep I accidentally set it free? The thought is too terrifying to consider.

But then she smiles. Her father is right. She does know this spell. She has known it by heart her whole life.

Carved into the rock face, glowing in the purple mist, are the lines of the poem her father used to say to her each night when he tucked her into bed.