Erling’s information was that Mark had been found in the river, and it was being trailed as a possible suicide. Something he hadn’t told Ava. Whether he’d been dead before he’d gone in or drowned would no doubt be established at post-mortem.

Erling broke into her thoughts to tell her that the evidence bags and the body from the beach were already at the airport. ‘With any luck, you’ll be back in your lab before lunchtime.’

‘That would be good,’ Rhona said.

They’d navigated Kirkwall by now and were heading out on the airport road. True enough, the mist was thinner here, as Erling had said it would be. Glimpses of sky suggested an elusive sun would hopefully burn it off.

‘I’ll have to get back to the station, so I’ll drop you at the door, if that’s okay?’ Erling said. ‘I’ve instructed Officer Tulloch to make sure you and the body get away all right.’

As they drew up outside the terminal building, Rhona thanked Erling for his help.

‘No bother,’ he said. ‘You’ll hear from me direct if your missing stowaway turns up. And we’ll look after Ava, I promise.’

Now, she had to find somewhere private to try to contact Ava. The airport was a size that befitted the islands’ population. Glasgow it was not. Open-plan, with a small cafe, a few tables, the rest of the area taken up by seating for the waiting passengers.

Rhona had a quick glance around and spotted Ivan Tulloch right away, even as he noted her own entrance. There would be no hope of talking privately to Ava with Ivan by her side.

She gave the police officer a little wave of acknowledgement, then indicated she was heading for the Ladies. Once inside, she chose a cubicle, went in and locked the door.

Ava’s mobile rang out, but went unanswered. Rhona stopped the call, waited a few moments then tried again. If Ava wouldn’t answer her, what could she do?

Her frustration was eventually curtailed when the call was picked up.

‘Yes?’ an Orcadian male voice said, who she presumed must be Dougie.

‘It’s Rhona MacLeod here,’ she said. ‘May I speak to Ava, please?’

‘Ava’s not here,’ came the terse reply.

That seemed odd, Rhona thought. Where would she have gone without her mobile?

‘When will she be back?’ she tried.

‘No idea,’ he said rudely, and hung up.

Emerging from the toilets, Rhona saw PC Tulloch waving her over.

‘The helicopter’s here and loaded. Would you like me to walk you out, Dr MacLeod?’

Rhona gave him a smile. ‘That won’t be necessary, Officer Tulloch. Walking across the tarmac’s the easy part. It’s the flying bit that’s the problem.’