They knew it would be a rush to get there and back that evening. The last ferry north to Unst on a Friday night was always busy, so they’d want to avoid that. It would be full of kids who’d been to parties or down to friends in Lerwick. Couples who’d made the trek south for the sort of dinner out they’d not get in the North Isles. And late in the evening there’d be fewer ferries. The last thing they’d need would be to be stuck in Yell, or having to leave the car there and come back as foot passengers. And if Monica split her time between London and Shetland there was no guarantee she’d be there.

‘Perhaps we’re better leaving it until the morning,’ Perez said. The only contact they had for Monica Leaze was at the gallery, and it was possible that nobody was there at this time. Of course Sandy should be able to track down a home address for them before they arrived in Yell. Mary Lomax would probably know. But Perez hated the idea of turning up at the artist’s house, breathless and ill prepared. She was crucial to the investigation, and she was famous. It seemed the worst kind of rudeness to barge in on a Friday night.

‘We don’t have time to wait,’ Willow said. ‘It has to be this evening.’ He knew she was desperate to move the case forward before the soothmoothers left the islands. He saw that there would be no reasoning with her.

Still, in the car at the ferry terminal in Belmont he had another go at persuading her to put off the visit until the following day. ‘Perhaps we should speak to Polly and Caroline first. Eleanor might have spoken to them about Monica. Or she might have dropped a hint that this wasn’t her first trip north.’

But now he saw that Willow was caught up in the moment of the chase. She was enjoying the frantic drive to the pier, and the sense of movement was a reaction to the frustration of sitting in Springfield House running through the details of the case in her head. Perez thought again that she was obsessed by the passing of time; this was her attempt to stop the clock.

‘We can’t piss about, Jimmy. This might be our breakthrough.’ Her eyes were gleaming. She was like a skua about to dive on an injured lamb.