The door creaks sooner than I expect.

‘Karl?’

‘Hetty? You’re still awake.’

‘Can’t sleep.’

‘I wondered. Listen, I have something for you. To make you feel better. I was saving it for your birthday, but I want to give it to you now. I’ll get you something else for your birthday.’ He snaps on the light and I blink at the sudden brightness.

Karl scrabbles under his bed and emerges with a brown, rectangular paper bag.

‘Here,’ he says, placing it on top of my blankets as I push myself up to sit. He perches on the edge of my bed. His cheeks are pinched and his forehead wrinkles beneath his dark fringe.

‘I wish I’d saved you today, Little Mouse,’ he says, ‘but I was too far away.’ I know he means it because, as he looks into my eyes, I can see straight into his soul. The worry has made his pupils huge and black and I can tell he’s crying inside, like me. I nod so he knows I understand.

‘At least Walter was there. And he is your best friend.’

I look at the paper bag, bulky in my hands.

‘Open it then,’ he urges.

The paper crackles as I uncurl the folded bag. I slip my hand inside and my fingers brush the hard cover of a book. It’s a journal, the type a grown-up might have. The front is covered with a rich patchwork of shapes in different shades of browns, oranges and blues. The paper inside is creamy white.

‘It’s beautiful,’ I whisper. ‘Thank you, Karl.’

‘There’s something else in there too.’ Karl smiles.

Resting at the bottom is a silver and blue fountain pen.

‘I thought you could write all your secrets in there. Or stories you make up with that wild imagination of yours,’ Karl says, searching my face.

‘I’ll try and write some really good ones. But maybe not about drowning.’ I smile at him. I want him to know everything is okay.

As I settle my head back on the pillow, I know that it is okay, but some things are changed.

I nearly drowned and Walter rescued me.

That makes everything different.

Part I

7 August 1933

‘Metamorphosis!’ exclaims Dr Kreitz. ‘That’s what the English call this book.’ And he waves its pages in the air with a flourish. ‘Can anyone tell me what that word means?’ He leans on the teacher’s table, shirtsleeves pulled up to his elbows. Not one of us makes a sound from our wooden benches in my new classroom at the Gymnasium.

No more dusty, higgledy-piggledy Volksschule for me. The small, black cinder playground and rough children are a distant memory from before the long summer break. The Gymnasium is all high arches and echoey corridors. In its centre, a great hall with a high, beamed ceiling beneath its grand, red, mansard roof. Here, the teachers are taller, smarter, stricter. I might have got better marks in the entrance test than Karl did three years ago, when he sat for them like me, at eleven, but now I’m here, I don’t feel very clever at all.