‘Oh, I see,’ says Sylvie on the other side of the door. ‘You don’t need to use Welsh. What a clever baby magician.’

The pantry fills with clammy, stinking fog. I gag and push open a small window. Fresh, cold air rushes in.

Let me in! I hear Sylvie think.

‘Spell. Clear fog,’ I say, and the fog evaporates.

‘Doing spells in English is terribly impressive,’ says Sylvie. ‘But your mother is out here alone, Tulsi. Oh dear, she looks rather unwell.’

I feel a blast of burning anger. Can this Sylvie really be so evil?

‘She’s no use to you if she dies,’ I say.

‘She won’t die,’ says Other Sylvie. ‘But she’s not the one I need. I need you.’

Well, you’re not getting your hands on me. I say, ‘Spell. Cloak of silence,’ then lift myself onto the window sill, climb through and drop barefoot into the knee-deep snow.

There’s no sign of Sylvie, but surely she can tell I’m not in the pantry anymore.

Keeping low, I make my way around the cottage and peek in the living room window. Mum is on the couch, eyes closed, completely still.

I hold up my hand up to the window and try to beam energy at her. I don’t know whether it will work, but it’s safer than going back inside. After about ten seconds, her skin pinks up. She sits up and looks around the room, eyes wide. I tap on the glass and she smiles with relief. Then her eyes widen in fear.

I turn around.

Sylvie stands in the snow behind me, a dozen small black birds perched on her head and shoulders. She is much taller than before; broad-shouldered, queenly. What magic is she using?

She smiles. ‘You’re not going to make it back to London in time. So we might as well talk about how I can help you. And how you can help me.’

‘I will never help you. I will do everything in my power to stop you.’ I blurt out the spell. ‘Swyn, mae dy hud yn diflannu …’

Sylvie’s face draws into an unearthly grimace. She points at me and speaks slowly, with intent. Welsh words that I don’t understand. My mind blanks. All I can do is repeat, ‘No, no, no. I will not let you.’

I feel the actual weight of Sylvie’s magic pushing against me. My vision starts to go grey and speckly. A clammy fog surrounds me, its fingers finding their way into my nose and ears and eyes. Her voice fades in and out. I cannot move my arms or legs, and a terrible thought comes to me. Is this what dying feels like? Is this my life force leaving my body?

Would Sylvie really kill me?