As I went through the ledgers I began to understand how involved Walter had become in the planning of Steiner’s commissions. He’d obviously become more important than just a hired hand. No wonder the job kept on pulling him back. I hoped Ernst was paying him properly – but then Walter was one of the few Bauhaus students who was never out of pocket.

At the bottom of the box was a painting wrapped in paper and string. I undid the bows, wondering what bucolic landscape it would reveal, but what I hadn’t expected was this painting in particular. I propped it against the wardrobe to take a better look at the September image which had stayed with me so vividly over the years: perhaps because of the image, perhaps because of the shiftiness that Walter had exhibited around it. It was from the week that Walter had disappeared.

And now here it was in all its glory, lit even better by the flashes of winter storm: the gabled cottage; the blur of orange chickens; the draught horse; and the three girls playing, looking apprehensively sideways.

The years gone had given me fresh eyes and it took me only a moment now to see its trick. There’s a painting by an old Dutch master – a big Netherlandish landscape, which looks on first viewing like a normal scene of canals, narrow boats, Dutch houses, until you realise the light is pouring in from two directions. Everything is light; nothing is unlit, and it’s not the high midday sun either, but a blast from east and west. It’s an impossibility, and somehow Walter had managed to achieve this same doubleness.

It was a lovely piece. It didn’t make sense that Ernst hadn’t sold it. The paintings that didn’t sell he simply used for firewood. Maybe Walter had convinced him of its sentimental value, but I couldn’t see why: it was only the technique that made it special, not its subject, and Ernst was only ever interested in subject.

‘What’s this?’

I hadn’t noticed Charlotte in the doorway. ‘A delivery for Walter,’ I said.

‘What is it all?’

I looked at the notebooks and old paintings on my bedspread. ‘Don’t know,’ I said. The dust made me want to sneeze. We hadn’t ordinarily been allowed to leave our things at the studio. But Walter, as he was proving, had always been a different case to the rest of us. ‘Remember this?’ I said, pulling out the bog painting she’d sold for salt.

‘Oh, God!’ she said, but she was laughing. ‘Don’t remind me! It’s awful! What’s it doing here?’

‘I’ve always thought it’s more interesting than you ever gave it credit for.’

‘For a frog, maybe. Is there another one? Didn’t I sell him two?’

‘Maybe Walter sold it.’ I looked into the box. ‘Its twin is gone.’