My voice spooked the birds from the branches. With the trees crowding in and each part of the park looking identical to the last, we had to admit we were lost – or, more precisely, that we had lost Charlotte. Impossibly, Flora appeared again. I knew the Georgium like the back of my hand; we both must have been incredibly drunk, because I couldn’t for the life of me work out where she’d gone.

It was then I noticed Walter’s pink freezing feet. ‘Walter! Where are your shoes?’

He looked at his bare feet, perplexed. ‘Oh, I must have lost them.’ He laughed. ‘I can’t really feel my feet.’

‘She’s going to freeze to death without a coat. And you’re going to get frostbite!’

We turned back to the mausoleum; stone bears growling, thorny-crowned Christ beckoning. At last at the river we saw a shape up on the bridge: Charlotte’s Liberty robes falling over the railings. She looked as if she was about to do something stupid, or that the river would catch the fabric and drag her down by the brooch at her neck.

‘Charlotte!’

We both ran toward the bridge, but she made no movement to acknowledge we were there. She kept her eyes on the quick dark river below, the dirty snow collecting at its banks. ‘Charlotte!’ Closer to, her skin was lavender. Her mouth was grim; her eyes, dead. ‘You’re going to freeze! Let’s get back.’

I heard Walter’s laboured breath behind me. When she saw us, she looked only at Walter. She still held her Liberty tablet. She brandished it at him, and I saw at once it was one of his navy ledgers.

‘What’s going on?’ I said.

‘You tell him!’

‘Where did you find this?’ he said, very pale.

‘How could you?’ she said, and it was almost a wail. ‘Oh, how could you!’

‘Please, can someone tell me what’s going on?’

But Walter was dumbstruck and would not speak. All the dreamy melodrama had gone.

Charlotte’s skin was goose-fleshed, her lips tinged blue. ‘Why don’t I explain? Here!’ She flicked to the back of the notebook and thrust it at me. There was a table, with numbers on one side, names in the middle column, and nationalities on the right. I saw her name, Charlotte Feldekova, and her nationality, Czechoslovak, to the right. The list continued: other foreigners’ names, and Jewish names in there, and probably some Communists too. I saw Masha’s name, and Stefan’s.

It was Walter’s handwriting. Slowly I realised what was happening; what it was that she was showing me. That September, in 1923, he had given all these names to the newspaper. It had published the story based on Walter’s information. He’d betrayed her.

He’d betrayed the whole school.