They talked with the churning of the dishwasher in the kitchen as a background to the conversation. Perez set a small tape recorder on the table between them. He’d borrowed it from Stella, the schoolteacher, when he’d gone down the island to store Angela’s body.

He nodded towards the machine. ‘You don’t mind? This isn’t a formal interview, but I don’t have anyone to take notes.’

Listening to the recorded conversation later, the background sound of the kitchen appliance, kicking in before the speech, would immediately make him feel uneasy and remind him of his struggle to ask the important questions.

He began with the factual details he already knew: he’d found guests’ names and addresses on the bird room computer and colleagues in Lerwick had already done a check for criminal records. Fowler’s was clean. The couple lived in Bristol. John was forty-nine and Sarah was forty-one. Now the man sat in front of him, quite unmoved, it seemed, by the situation. His hair was slightly long for a man of his age and he wore denims and a knitted jersey. There was nothing unusual or impressive about him. He was the sort of character always passed over in an identity parade.

‘What brought you to Fair Isle in the autumn?’ Perez asked.

‘Birds.’ Fowler smiled. ‘We’re just like the other mad people who come all this way. I’ve spent a couple of autumns in Shetland, but I’ve never been to Fair Isle. It’s been a dream, you know. For birdwatchers the place has an almost mythical status. It’s a place where almost anything can happen. And today it did, of course, with the trumpeter swan. Besides, Sarah needed a holiday.’

‘Why did your wife need a holiday?’

‘Does it matter?’ The smile vanished, replaced by a small frown, as if Perez had committed some unfortunate breach of manners.

‘Probably not.’ Perez wasn’t sure what had led him to ask the question, but now Fowler’s response intrigued him. ‘But I’m interested.’

Fowler shrugged. ‘She’d lost a baby. We’d given up hope of conceiving. Tried everything – had all the tests, IVF. Then there was that wonderful moment when she realized she was pregnant. But there was a miscarriage. Nobody can tell us why. Her baby would have been due this week. It’s been a strain for both of us. I had to get her away.’

‘I’m sorry.’ Perez’s first wife had been called Sarah too and she’d had a miscarriage. He’d thought it had been at the root of the breakdown of his marriage. Certainly he had never been more unhappy than when they lost the baby. Now he felt like an insensitive oaf for prying into private grief.

‘You won’t say anything to her.’ Fowler looked earnestly at Perez. He had the air, Perez thought, of an academic, gentle, a little unworldly.

‘Of course not.’ The dishwasher beeped to show it was at the end of its cycle. ‘Had you met Angela Moore before you came to the field centre?’