Under a clear April sky, though, this Scottish moor looked benign, empty and majestic. On closer inspection, Rhona could make out dark burnt patches among the heather and mosses, indicating it was being used for driven grouse shooting. Despite the intrusion of man, this was still a perfect spot – just like Saddleworth Moor – in which to hide a body that would never be found.

Whoever had buried the body she and Chrissy were preparing to expose could never have imagined that folk would be mad enough to ever wild swim in the neighbouring dark waters of Advie Lochan, never mind in early April.

Even then, had there not been a long dry spell – had the water level not fallen, exposing the bank and allowing it to dry out – there would have been nothing to see, even for the determined and curious wild swimmer, which had been Bill’s description of the young woman who’d alerted the police to her find. Despite the shock, Julie had fetched her mobile and, swimming back, had taken a number of images to back up her gruesome discovery.

Rhona had already set up the time-lapse camera, with a cover to protect it from any change in the weather. Although, according to the forecast, there was a chance that they might avoid rain for the next twenty-four hours.

Once they were ready to begin, she would set the camera to take an image every ten minutes of excavation. That sequence of shots would eventually be put together as an MP4 video, which she could use in court if required. This type of work required daylight, so that the different-coloured layers of the soil might be registered, hence no forensic tent.

En route to the locus, Rhona had called Jen Mackie, her forensic soil scientist colleague, regarding their destination and had discovered that the co-ordinates of the locus were likely to be in an area of raised bog. If true, that would affect what they might find during the excavation.

‘I was involved with the Woodland Trust in 2012 surveying areas of raised bog across Scotland,’ Jen had told her. ‘Where you’re heading is one of the areas we mapped. I’ll email you the report. It makes for interesting reading.’

Rhona had put the call on speaker in the car, so Chrissy might listen in.

‘So what does that mean exactly for the state of the remains?’ Rhona had asked.

‘The chemistry of raised bogs would suggest you may find more than just a skeleton. I’ll be in touch when I get back from Paris,’ Jen had promised. ‘I’m currently being driven through the streets in an armed police convoy to give evidence in an enquiry.’

At this news, Chrissy’s eyes had lit up.

‘When can I go to Paris to give evidence?’ she’d whispered.

‘When you come to work for me,’ Jen had told her with a chuckle, having obviously heard Chrissy. ‘You’ll send me images?’

‘I will,’ Rhona had promised.

At that point, Jen had wished them good luck before they’d heard the whine of a siren, and she’d rung off.