Perez recognized the song after the first few bars. Cassie had learned it at school and had come home singing it, over and over, to rehearse for the end-of-term show, until he and Fran had wanted to scream. And although Fran was still alive then, still a real presence in her own house, warm and strong and argumentative, he’d thought it wrong to teach Peerie Lizzie’s song to the children. He’d understood the need for the bairns to be aware of their cultural heritage, the folk traditions, but this song had only been written twenty years ago, by Marty Thomson up in Northmavine, and it celebrated the death of a real child who had died. But when he’d voiced his concerns to Fran she’d laughed at him and told him he was being daft and he’d spent too long as a cop. ‘Kids love spooky stories. And most of them don’t even listen to the words.’

His sense of her was so real that for a moment he imagined it was Fran sitting on the other side of the desk in the big house in Unst, and not Willow Reeves.

On hearing Willow’s voice he was jolted back to the present, and felt the loss of his woman all over again. He felt he had to explain his reaction to the song, and as he did so his memory of Fran’s laughter at his anxiety – at his notion that Cassie might be frightened – melted away. He’d wanted to focus on the memory, the sound that Fran’s voice had made and the shape of her body with her head thrown back.

‘A well-known local musician wrote it. It’s a kind of ballad, using the story of Elizabeth Geldard’s death. The children learn it in school – it’s seen as part of their heritage, but the teachers also use it as a warning that the shore can be dangerous and the children have to be aware of the incoming tides.’ As he spoke he was thinking there was something different about the song on the tape. It wasn’t quite as Cassie had sung it. He considered asking Willow to play it once more, but was worried about the way he might respond. Perhaps he’d get emotional again, break down even, and he’d promised Willow that he was well now and perfectly fit for work.

‘So why is it on Eleanor’s recorder? Did Vaila Arthur sing it? More background to her story of seeing the ghost?’

‘That wasn’t a woman’s voice,’ Perez said. ‘It was a child.’ It was the one thing of which he was certain.

‘So if we find out who the singer was we might know who else Eleanor met on the day of the party. Vaila only has a baby. It couldn’t have been her.’

Perez didn’t answer.