‘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.

Fran’s parents were waiting for them, had probably been looking out for the taxi for hours. Cassie was their only grandchild, but it was more than that. She was all they had left of their daughter. Perez could understand why she was so important. They glimpsed traces of the girl they’d known and the woman they’d lost in Cassie’s eyes, in the way she ran, and in her stubbornness and her fierce independence. They lived in a neat little house in a tree-lined suburb, which had become more fashionable since they’d bought it. There was a new coffee shop on the corner. A woman in an extravagant floral dress walked down the street clutching a small white dog and ignored them.

Fran’s mother took Cassie to the room that had once been Fran’s. It smelled of paint. Perez wondered if the couple had been up all night decorating it. There was a view over city gardens, and everything was green and lush.

‘You’ll stay for an early supper, Jimmy? I thought we’d eat soon because Cassie will be tired.’ She smiled and he thought she was a very good woman. She made such an effort to keep the blame from her voice.

‘I’m sorry,’ he said. ‘I’m pushed for time. You know.’