He’d smiled then. ‘Isn’t that a sort of busman’s holiday?’ But he’d gone online to look at timetables and book ferries very quickly and they left almost at once. She thought that he was always happier when he was moving. He talked about settling down and finding a job that would keep him in the country for more than a month at a time, but she thought he’d soon get restless. They’d asked Ian if he’d like to join them, but he refused and Polly sensed that he was pleased to see them drive away. In the house on the beach they were like rats crammed together in a cage.

Lerwick felt like a big town after Unst. The boat to Aberdeen was moored at the ferry terminal. It looked huge, a reminder of the mainland, real-scale cities and real-scale transport. Polly looked at Marcus, wondering if he’d had the same thought as she’d had: they could just drive aboard and escape completely. But he seemed not even to notice it and had his eyes on streets and road signs, and was triumphant when he brought her straight to the new buildings of the arts centre and the museum looking out over the water.

‘What will you do?’ She knew that the museum would bore him. He was only interested in the exotic present.

‘I’ll explore the town. Meet you in the cafe back here for tea? Then I suppose we’ll have to get back.’

‘We could book into a hotel for a night.’ The thought of returning to Unst and the house by the shore already made her feel panicky. She imagined a solid town house in Lerwick, a meal in a good restaurant, then frivolous television in their room. Something to banish thoughts of Eleanor.

He looked at her and she could see that he found the idea appealing too. For a moment she thought he might agree to the plan. ‘Perhaps we’d better not,’ he said at last. ‘We don’t want the police to think we’re being difficult.’

In the main body of the museum there was a small display about Elizabeth Geldard and an oil painting of the girl, sitting at a window, with her hands on her lap looking very demure. She wore winter clothes, a knitted cardigan and a hat, and it was only the long hair that made Polly think of the girl she’d seen on the beach. This child looked rather staid and dull, and Polly couldn’t imagine her twirling on her toes or skipping across the sand. There was no mention of the acquisition of the work, whether it had been a donation or been purchased. A small display board explained the legend of Peerie Lizzie, but Polly learned nothing new from it, except that a song about the girl had been written by Marty Thomson, a local musician.