On the way south to Sumburgh they talked about London. ‘Grandma wants to show you the sights,’ Perez said. ‘She’s talking about a boat trip on the Thames and all sorts of treats. They can’t wait to see you.’

‘Will you be there?’

‘I have work to do in the city,’ Perez said. He paused. ‘Anyway I think Grandma and Grandpa would rather have you to themselves for a while. Then they can spoil you without me seeing and stopping them.’

‘Is it dangerous work?’

‘No! It’s talking to people, to women mostly. Routine. Background stuff.’

‘But you’re a boss,’ she said. ‘Sandy should be doing routine work.’

‘I wanted an excuse to take you to London.’ And that, at last, seemed to satisfy her.

It was a clear day and, on the flight south to Aberdeen, Fair Isle appeared suddenly beneath them, with the iconic shape of Sheep Rock to the east. Perez wasn’t sure whether he should point it out. That’s where I was born. And where your mother died. But Cassie saw the island below and mentioned it herself. ‘You said you would take me soon,’ she said. ‘When can we go?’

‘This summer. When school’s finished. We’ll stay for a few days.’ He realized that the idea made him uncomfortable. Was it impertinent to think of Cassie as belonging to his family now? What would Fran’s parents in London make of that?

Cassie seemed to pick up his ambivalence. ‘What should I call your mother and father when I see them? They’re not quite grandparents, are they? Or are they? I never know, so I end up not calling them anything.’

‘They think of themselves as your grandparents,’ he said. But call them whatever you like. James and Mary? You could ask them.’

She peered out of the window until the island disappeared from view. There was a quick connection at Aberdeen and then they were arriving into Heathrow, into the crowds and the noise. Everything giant-sized and everyone yelling. Cassie went very quiet and held onto his hand. She looked smaller here where the buildings and the buses towered above her. He wanted to scoop her up in his arms and take her back to Shetland, where he could keep her safe. Then he thought that a woman had just been killed in Shetland and that people were much the same wherever they were.