In the car back to the ferry terminal Perez was on the phone to Sandy. More requests. ‘Can we rouse someone at NorthLink and Flybe and see if Monica Leaze left Shetland on the day of the murder. Or the day after. The Sunday. It’d also be great to find out if Eleanor met her on her flying visit to Shetland the week before. I think Monica is friendly with the director of Shetland Arts, so Mareel might be a logical place for them to meet. Do you know any of the kids who work in the bar there? See if they remember the two women meeting. They’d have stood out. Both English, both stylish.’ He paused for breath and imagined Sandy jotting down notes, rather slowly, on a scrap of paper. ‘Did you get all that, Sandy?’

‘I went to see George Malcolmson,’ Sandy said. ‘I had an idea.’

‘What idea would that be, Sandy?’ Perez was glad that he was on the phone. The mood she was in, Willow would already have lost her temper with the younger man.

‘I was talking to Louisa about the fact that she was adopted. I wondered about Lizzie Geldard.’ He paused and Perez didn’t make any attempt to hurry him. Sandy would need time to gather his thoughts. ‘It seems she was the natural child of Sarah Malcolmson. Story is that Gilbert Geldard seduced the girl when she was only fifteen. Roberta took in the little girl, not knowing the history. I wondered how she’d feel about the girl if she found out the truth.’

‘You think Roberta might have drowned Lizzy Geldard?’

‘I don’t know.’ Sandy sounded anxious and worried that he was making a fool of himself. ‘What do you think?’

‘I can see how that might happen.’ Perez thought that an angry woman might blame the child, rather than the man she would be forced to stay married to for appearances’ sake. If Gilbert had loved Lizzie because she was his daughter, to kill her would be a terrible act of revenge. And a denial – a way of eliminating the proof of her husband’s flaws.

‘I don’t see how it could have any relevance to this case, though,’ Sandy said.

Perez didn’t answer. He was thinking that the heart of the investigation lay in complex families trying to survive.

‘How have you and Willow got on?’ Sandy asked. ‘I booked you onto the last ferry. Are you heading back now?’ He sounded nervous.

‘It was very interesting,’ Perez said. ‘We’ll fill you in when we get back. We’re hoping to get the earlier ferry, so we should see you soon.’