‘I knew what it meant as soon as I saw it,’ he went on. ‘Mrs Baron went very quiet after Michael went missing, though. The deliveries to London seemed to stop altogether, so there was no chance of catching her red-handed. And you won’t believe the trouble I had trying to get a warrant to search a magistrate’s house. It was only after your sister came to the police station yesterday and Michael was arrested that we were finally granted permission to search the property.

‘We found some papers belonging to her late husband; a Nazi flag, which they were intending on flying from their window in the event of an invasion; a radio, and a set of instructions for signalling to the U-boat. That note had yesterday’s date on it. When I saw that the lighthouse was indeed part of her plan, I came up to the Castle straight away. And the rest you know, Petra.’

‘Yes.’ The rest I knew.

I watched a young seagull launching into the air, gliding all the way down from the top of the lighthouse, over the raw edge of the cliff.

It had been hard to get used to that new gap on the clifftop where the bomb had fallen. It reminded me of the jagged tear across the middle of our family tree – Pa and Mutti ripped away from us, just the daughters left behind, so close to the edge . . .

‘Do you think they will ever let Mutti come home?’ I said.

‘At some point. Provided the authorities believe she is no threat to security. It seems that her cousin in the Gestapo was killed by resistance fighters in France last month.’

I took in a little sharp breath. ‘You knew about him?’

‘Yes.’ He nodded. ‘And I know that your mother’s communication with him was entirely innocent. It seemed that she was still fond of the little boy she remembered from childhood; she had no idea about the sort of man he had become. It would really be something if her annual Christmas card message of Frohe Weihnachten! turned out to be some kind of complex code.’ The lines of his face folded into a smile. ‘Your mother was convinced that Magda was in trouble – did you know that? She had asked her where she was going so early in the mornings and Magda had lied to her – said she was working on the motor boat at the harbour.’

‘She didn’t want us to know about Michael.’

‘No.’

It was all making sense now. ‘Mutti suspected Mags had got involved with something bad, didn’t she? That was why she wanted us both to be evacuated.’

‘Yes.’

‘And that was why she confessed to being a spy. She had no idea it was Pa who’d actually sent the documents – she assumed it must be Mags. She was trying to protect her.’

‘That’s right.’