Thorne jabbed at the buttons on the phone. He’d only signed out for two hours, so now he needed to let them know that he wouldn’t be back until sometime the following day. He’d have been happiest leaving a message, but he was connected straight through to Detective Sergeant Samir Karim in the Incident Room.

‘You must be psychic.’

‘Sorry?’

‘The DCI’s in the middle of leaving a message on your phone.’

Thorne reached into his jacket for his mobile. He’d turned it off in the hospital and forgotten to switch it back on again. By the time the screen had come back to life and the tones were sounding to indicate that he had a message, Detective Chief Inspector Russell Brigstocke was on the landline.

‘Good timing, mate. Or bad.’

‘What?’

‘We’ve just caught a job.’ Brigstocke took a slurp of tea or coffee. ‘Nasty one, by the sound of it.’

Thorne swore quietly, but not quietly enough.

‘Look, I was about to give it to Kitson anyway.’

‘You were right before,’ Thorne said. ‘Bad timing.’

‘It’s yours if you fancy it.’

Thorne thought about Louise, what the woman had said about needing to take things easy. Yvonne Kitson was perfectly capable of dealing with a new case, and he had plenty on his plate at work as it was. But he was already on his feet, hunting for a pen and paper.

Elvis was mooching around his ankles while Thorne scribbled a few notes. Brigstocke was right, it was a nasty one, but Thorne wasn’t overly surprised. It was usually The nasty ones they put his way.

‘Husband?’ Thorne asked. ‘Boyfriend?’

‘Husband found the body. Made the call, then ran out into the street screaming the place down.’

‘Made the call first?’

‘Right. Then lost it, by all accounts,’ Brigstocke said. ‘Banging on doors, telling everyone she was dead, screaming about blood and bottles. Definitely not what the good people of Finchley are used to.’

‘Finchley’s easy,’ Thorne said.

‘Right, nice local one for you.’

Five or six miles north of Kentish Town. He’d be more or less driving past the Whittington Hospital. ‘I’ll need to make a quick stop on the way,’ Thorne said. ‘But I should be there in half an hour or so.’

‘No rush. She isn’t going anywhere.’

It took Thorne a few seconds to realise that Brigstocke was talking about a dead woman and not about Louise Porter.

‘Give me the address.’

It was a quiet street, a few turnings east of the High Road. Edwardian houses with neat front gardens and off-road parking. Many, like number 48, had been divided into flats, though this house was now itself divided from its neighbours: a tarpaulin shielding the side-alley, uniformed officers stationed at each corner of the front lawn and crime-scene tape fluttering above the flower beds.

Thorne arrived just before eight, and it had already been dark for almost an hour. It was light enough in the kitchen of the downstairs flat, where the beams from twin arc-lamps illuminated every mote of dust and puff of fingerprint powder, bounced off the blue plastic suits of the CSIs and washed across the linoleum on the floor. A retro-style, black-and-white check, its simple pattern ruined by a few spots of blood. And by the body they had leaked from.

‘I think I’m about ready to turn her,’ Phil Hendricks said.

In the corner, a crime scene investigator was scraping at the edge of a low cupboard. She barely glanced up. ‘That’ll be a first…’

Hendricks grinned and gave the woman the finger, then looked around and asked Thorne if he wanted to come closer. To squeeze in where he could get a better view.

Thorne doubted that the view would get any better, but he walked across and placed himself between the still- and video-camera operators, opposite the pair of CSIs who were preparing to give Hendricks the help he needed. To add the necessary degree of strength to his gentleness.

‘OK, easy does it.’

The woman was face down, arms by her sides. Her shirt had been lifted, or had ridden up, showing purplish patches on the skin just above her waist where the livor mortis had started and revealing that her bra had not been removed.

‘Something, I suppose,’ a female CSI said as she walked past.

Thorne raised his eyes from the body and looked towards the single window. There were plates and mugs on the draining board next to the sink. A light was flashing on the front of the washing machine to let somebody know that the cycle had finished.

There was still a trace of normality.

Assuming they didn’t get a result in the first few days, Thorne would try to come back at some point. He found it useful to spend time where the victim had lived; even more so if it was also where they had died. But he would wait until he didn’t have to weave between crouching CSIs and negotiate the depressing paraphernalia of a crime scene.

And until the smell had gone.

He remembered some movie where the cop would stand in the houses where people had been murdered and commune with their killer. Was this where you killed them, you son of a bitch? Is that where you watched them from?

All that shit…

For Thorne, it just came down to wanting to know something about the victim. Something other than what their last meal had been and what their liver weighed at the time of death. Something simple and stupid would usually do it. A picture on a bedroom wall. The biscuits they kept in the kitchen cupboard or the book that they would never finish reading.

As for what went on in the mind of the killer, Thorne was happy knowing just enough to catch him, and no more.

Now, he watched as what remained of Emily Walker was moved, saw the hand flop back across the leg as it was lifted and turned in one slow, smooth movement. Saw those strands of hair that were not caked in blood fall away from her face as she was laid down on her back.

‘Cheers, lads.’

Hendricks worked with a good team. He insisted on it. Thorne remembered one CSI in particular – back when they were content to be called scene of crime officers – handling the partially decomposed body of an old man no better than if it were a sack of spuds. He’d watched Hendricks pushing the SOCO up against a wall and pressing a heavily tattooed forearm across the man’s throat. He couldn’t recall seeing the two of them at the same crime scene since.

The cameramen stepped forward and went to work. When they’d finished, Hendricks mumbled a few preparatory notes into his digital recorder.

‘How much longer, Phil?’ Thorne asked.

Hendricks lifted one of the dead woman’s arms; began bending back the fingers of a fist that was closed tight. ‘Hour and a half.’ The thick Manchester accent stretched out the pathologist’s final word, flattened the vowel. ‘Two at a push.’

Thorne checked his watch. ‘Right.’

‘You on a promise or something?’

Thorne did his best to summon the right expression, something conspiratorial and devilish, but he wasn’t sure he’d managed it. He turned to see where Detective Sergeant Dave Holland had got to.

‘She’s got something in her hand,’ Hendricks said.

Thorne turned back quickly and bent down to get a closer look, watched as Hendricks went to work with his tweezers and lifted something from the victim’s fist. It appeared to be a small square of plastic or celluloid, dark and wafer thin. Hendricks dropped it into an evidence bag and held it up to the light.

‘Piece of film?’ Thorne asked.

‘Could be.’

They stared at whatever was in the bag for a few more seconds, but both knew they would only be guessing until the Forensic Science Service laboratory had finished with it. Hendricks handed the bag over for the evidence manager to log and label, then carefully fastened polythene wraps around both the victim’s hands before moving further up the body.

Thorne closed his eyes for a few seconds, let out a long breath. ‘Can you believe I had a choice?’ he said.