He knocked at the classroom door and went in. There was a smell of poster paint, clay and floor polish. They were sitting around tables in rough age groups. The older ones were working from maths sheets. Louisa was squatting with the little ones, helping them build a model from cardboard tubes.

‘Yes.’ She got to her feet. Then she saw him. ‘Sandy Wilson, what are you doing here?’ Her voice was cool. He might have been one of her seven-year-olds misbehaving.

‘I’m working on an investigation into a serious crime,’ he said. ‘Perhaps you’ve heard about it.’ He was aware that the older children were listening in.

‘I’m not sure how I can help.’ She had smooth, dark hair and he thought she had more in common now with the English people in Sletts than she did with him. He was pleased that she’d known him at once, though. He’d wondered if she would have forgotten him.

‘Perhaps I should come back later,’ he said, ‘when you’re not so busy.’

‘No need for that.’ She watched a car pull up outside. ‘That’s Mr Rickard. He’s here to take music – that’s one subject I can’t teach, even to the little ones. You remember me, Sandy, always tone-deaf, always told to stand at the back and mime.’ She turned her attention back to him and smiled. ‘If you’re lucky I’ll make you a cup of tea and you can tell me what this is all about.’

She asked the children to finish what they were doing and he looked around the room. As Davy Stout, the ferryman, had said, there was a preponderance of boys. He couldn’t see any girls with long, dark hair. This would be a waste of time and he’d have nothing to tell Perez to make him proud.

They drank tea in a little room that acted as her office.

‘What brought you back?’ he asked.

She shrugged. ‘My father died last year and my mother’s on her own. Guilt, I suppose.’

‘You had nothing to keep you south?’

‘I don’t have a husband or a family, if that’s what you’re asking.’

He thought she’d always had a sharp tongue. It’d be a brave man who took her on.

‘So what are you doing in Unst, Sandy Wilson? And in my school?’

‘The woman who was killed, she had a thing about Peerie Lizzie.’

‘What sort of thing?’ She took a biscuit from the tin that stood between them and dipped it into her tea. Her teeth were very sharp too.