She found a copy of a file on her desk. There were photographs, so far out of proportion that they looked huge and disorientating. The Forensic Science Service laboratory had performed wonders getting fingerprints from Nadezda Halak’s hand, processing the sloughing skin sufficiently to provide a strong possibility of a match if her prints were on record. It couldn’t have been easy, teasing out an identifiable print from a fragment of rotting hand. The entire thumb was gone, and so were half of the index and middle fingers. The skin that remained had been decomposing and so fragile that it had to be soaked in alcohol to toughen it up and draw out the water.

But under twenty times magnification in the scanning electron microscope, traces of damage to the bones of the hand were just about visible, along with fractures at the surface where the cartilage had been attached to the central arch. Magnified a hundred times, the damage was unmistakable – linear fractures ending in a small region of crushed bone. There were no signs of healing, which indicated that the fracture had occurred perimortem – at, or just before, death.

Instead of finishing her report, Fry phoned the Forensic Science Service and asked to speak to one of the chemists who was dealing with evidence from the abandoned meth lab at Pity Wood.

‘Yes, methamphetamine production in a makeshift laboratory is a very dangerous activity, unless you have training as a chemist,’ she said.

‘I think we can take it that the people involved at Pity Wood didn’t have that training, Doctor.’

‘Well, if an operator without proper training allows the red phosphorus to overheat – due to lack of adequate ventilation, perhaps – then phosphine gas can be produced. If it’s produced in large enough quantities, the gas usually explodes. Technically, the conclusion would be auto-ignition from diphosphine formation, caused by the overheating of phosphorus.’

‘Thank you.’

Fry put the phone down. Training as a chemist? The idea was enough to make anyone laugh. Illegal workers like Nadezda Halak, paid a pittance and hardly daring to go out in daylight for fear of being seen? Their instructions would have been basic, their understanding of what they were involved in even less, perhaps.

In other circumstances, Fry would have said that it was a mistake to assume innocence, just because an individual was dead. It was possible to be guilty and a victim at the same time. But she could never believe it of Nadezda and her fellow workers at Pity Wood.

Cooper came in, accompanying DI Hitchens after a visit to Edendale District General Hospital, where Raymond Sutton was being treated.

‘Mr Sutton isn’t in good shape,’ said Cooper, chewing his lip nervously. ‘They’re very worried about him on the ward. He wasn’t strong to start with. If one of the care assistants hadn’t been passing his room, he would have been dead a few minutes later.’