‘So what can it be, then?’

‘Embalming. That’s my guess.’

Perry sighed. ‘So our perpetrator isn’t only forensically aware, good with mobile phones and electronics, but also knows how to preserve a corpse.’

‘Maybe time to check out funeral directors,’ Gillard said.

Boatswain Chris Marshall steered his Zodiac inflatable expertly along the edge of a mass of tangled tree boughs and branches that seemed to embrace the full width of the river. He was about a mile downstream from Lacey Dutton, and had that morning been involved in the recovery of seven cars, vehicles that had originally been jammed against the arches of various bridges, but as the water level had dropped had the space to float through to the next obstruction. A few had even made it over the weir. Fortunately, none of them had contained a body. What he was working at now was potentially more troublesome, with too many underwater obstructions to allow the inflatable to make any progress. Divers from Police Scotland had been working all morning, picking through this great Sargasso mat of detritus, much of which had accumulated against a fallen riverbank sycamore. The huge tree, well over 200 years old, had acted like a giant net, hooking in everything that would float: fence panels, broken caravan sidings, polystyrene, and enough pub garden furniture to host a wedding reception. For those underwater, it was dangerous and awkward work, always the risk of a tree rotating and trapping a diver. The water beneath was still thick with silt and visibility was non-existent.

Marshall saw that one of the divers had raised his hand. He seemed to have made his way almost to the middle of this tangled mass. He was pointing at something and beckoning, but Marshall couldn’t bring the Zodiac any closer to get a better view. The frogman moved, clambering partially onto a submerged bough. His weight rotated the entire floating tree. As his side dipped, on the far side of the trunk another branch lifted, dripping from the river. Hooked over it a second arm could now be seen. This one was not sheathed in a wetsuit, but bare, pale and slender. It lifted in a balletic arc, a graceful female hand giving the briefest flick of acknowledgment, before it slipped between the twigs and slid back into the water.

Chris Marshall knew whom he was searching for. In his remembrance of this moment years afterwards he would sometimes wonder whether he had imagined the hand grasping a violinist’s bow, or whether what he had seen was simply a long twig, caught between her lifeless fingers.

PC Lynne Fairbanks and DC Carl Hoskins stood outside the front door of 16 Wensleydale Walk, Woking and surveyed the drive from which Kyle Halliday had attempted to save his two-year-old Mitsubishi Warrior from being stolen. It was late afternoon, just over a week after the incident. They pressed the doorbell, and the victim himself eventually opened it. He was leaning on a metal crutch, wearing jeans and a loose checked shirt. His left wrist was still bandaged, his right ankle too.