The weather had reverted from heavy rain to spring sunshine. The drenching had brought the moor to life, as though the prolonged downfall had been exactly what the mosses and heather had craved.

Having agreed that DS Strachan could leave the locus the previous evening, all that was left of their excavation was a roped-off area.

The grave was part-filled with water from yesterday’s rain, with softened peat reshaping the sides she and Chrissy had so carefully dug out. Rhona wasn’t concerned by this. They had, she believed, retrieved all the evidence that had lain there.

Making her way onto the small stretch of sand that bordered the northern end of the lochan, Rhona undressed and pulled on her short wetsuit, before fixing her head torch and wading into what felt like ice-cold water.

The little stream she’d watched spring to life with the downpour had dwindled again in strength, but the water it had fed into the lochan had raised the level by at least half a metre.

As the water filled her wetsuit, Rhona felt a warm layer begin to form. Wading further in, it took only a metre before she had enough water to swim. She stopped after a couple of strokes to feel again for the bottom, but it was no longer there, indicating the probability that the lochan had a deep core.

She suspected, once she’d dived a little to confirm this, that the incoming stream, when in spate, had succeeded in carving out the peaty soil from the deepest area, and what she could see and touch there was in fact bedrock.

Moving towards the bank that lay between her and the grave, she had to submerge again to look for the cavity that had housed the tangled roots interwoven with the fingers of the victim. Filled again with soil, had she not mapped its location, she would never have identified its position.

As Chrissy had said, the window of opportunity in which the body might be discovered had been small, relying as it had done on the long spell of unseasonably dry weather, plus the presence of a wild and curious swimmer.

Rhona, diving again, began to slowly map out the underwater world of the lochan. What she was looking for she had no idea. If asked, she could have only declared it as a hunch. But, as Magnus Pirie often said, intuition was just psychology in action.

Ever since she’d acknowledged, to herself at least, that the outfit and the victim were possibly not a match, Rhona couldn’t avoid the thought that more than one child might be involved. Maybe the Saddleworth Moor episode had influenced her thinking on that. Then again, child killers rarely stopped at one child, and generally went on killing until caught. And Mary McIntyre’s abductor had never been identified, let alone apprehended.

If she gleaned any evidence to suggest there might be more than one gravesite in the location then she could ask for a fuller search of the surrounding area. Recent advances involved using small unmanned aerial vehicles (UAVs) for aerial photography, which could examine the surrounding area for anomalies. Nutrient flush might be spotted where greener grass had come about because of leachate, a product of water passing through a deposition site.