Hugh shrugged. ‘To be honest, it was never going to be a long-term thing, was it? I mean, I can’t imagine we’d have kept in touch once I’d left the Isle. I’m sorry she’s dead, but I can’t pretend to be devastated. I can’t bear shallow sentimentality.’

Perez wondered if that was what he was. Sentimental and shallow. A brief affair followed by no contact didn’t fit his definition of being a good mate.

‘Did she seem anxious about anything? Concerned for her own safety?’

Perez had expected an immediate flip remark, but Hugh considered the question. ‘Something was bugging her,’ he said eventually. ‘The last couple of days she’d seemed tense, not her usual self.’

‘What was the problem?’

‘She wouldn’t talk about it,’ Hugh said. ‘Told me it was none of my business. That was OK with me. I didn’t want to pry. I thought the weather was getting her down. The lack of good birds. Or Poppy. The girl really got under her skin.’

‘Did she discuss her husband with you?’ Perez looked out over the blustery water. The air was so clear that he could see Shetland mainland, the outline quite sharp on the horizon, the first time it had been visible since they’d arrived on the island. He found the sight reassuring, a connection at last with the outside world. The next day the boat would go out and Vicki Hewitt and Sandy Wilson would come back in with it. He would no longer be working alone.

‘Oh, Maurice wasn’t bothering her,’ Hugh said with a little laugh. ‘Maurice would let her do whatever she wanted as long as she stayed married to him.’

‘He knew about her affairs?’

‘Probably. Or didn’t look too hard at what she was doing because he didn’t want to know. As I said, she resented Poppy being here. I think it was the first time Maurice had ever stood up to her. Angela had said the autumn was a bad time for the girl to visit – after the seabird ringing it was her busiest time. He’d insisted, said his daughter had to come first for a change. Angela was shocked. She usually got her way. But I’m not sure that was what was worrying her. It was only temporary, after all. Eventually the wind would change and the girl would get out.’

Hugh stood up and brushed the crumbs from his jacket. ‘I thought you wanted to see this swan.’ He turned on the inevitable smile and walked very quickly down the bank towards Golden Water. Perez had almost to run to catch up with him.

The swan was on a shingle beach at the side of the pool. It looked to Perez like any of the swans that came into the island in long skeins in the winter. ‘Show me what all the fuss is about,’ he said again.

Hugh set up his telescope on a tripod and let Perez look. ‘It’s the black beak that’s important. That and the American ring, which proves it hasn’t escaped from a collection somewhere.’ He straightened. ‘There’ll be hundreds of birders in Shetland mainland waiting to come here to see it.’