A passing SOCO/CSE followed Thorne’s eyeline. He nodded towards the rectangle of bare boards where the carpet beneath the body had been cut away and removed. ‘Central heating was cranked up, so he probably started leaking like a bastard after less than a week,’ the officer said. ‘Almost as much of him in the carpet as there was anywhere else. Gone right through.’ He pointed, keen as mustard. ‘Look, can you see?’

Thorne and Holland did, and could. The caramelcoloured blotch on the dusty boards was like damp behind a cistern.

‘Are you sure you want this one?’ Holland asked.

‘Already got it,’ Thorne said. ‘Brigstocke called when I was on the way over from Hornsey.’ He talked Holland through the PM, focusing on the headlines, finishing on Hendricks’ notions of what constituted a standard number of tattoos on an average used-car salesman.

Holland was unconvinced. ‘Hendricks has got a few more tattoos than your average pathologist.’ He counted them off, pointing to the appropriate point on his body as he did so. ‘That Arsenal thing on his neck. The Celtic band or whatever you call it on his wrist. That weird symbol on his shoulder. There’s probably a couple more that only his very good friends have ever clapped eyes on.’

‘I wouldn’t know,’ Thorne said. He stared hard at a SOCO working near by, a smart-arse he’d come across before who’d glanced over with something like a smirk.

They walked into Tucker’s kitchen. There was washing-up stacked next to the sink and the sheen of Luminol across the work surfaces. On their way out through the hallway they casually stepped over a fingerprint specialist working on a stretch of flaking skirting board.

‘Maybe it means something,’ Holland said. ‘That he waited before sending you that picture.’

‘Maybe it just slipped his mind.’ Thorne took the stairs two at a time. ‘You know what it’s like. You batter someone to death, take their photo, forget all about it…’

‘It might be significant, you know? Something about the day he chose.’

‘What? His birthday?’ Thorne turned to Holland, palms raised. ‘First Monday in the month? Let’s not forget how close it was to November the fifth. Maybe this bloke’s got a thing about bonfires.’

‘I was only thinking aloud.’

Thorne stopped at the door and took a breath. ‘Sorry, mate.’ There had been more anger than upset in Holland ’s tone, but Thorne still felt like a twat for being snappy. ‘Maybe he’s just another fucking mentalist, Dave. You know?’

Outside, Thorne stopped to talk to the video cameraman who was packing away his equipment, while Holland reached for cigarettes. A young couple with a pushchair appeared from between two unit vehicles and marched up to the crime scene tape.

The man leaned across and shouted to Thorne: ‘What are you filming?’

Holland opened his mouth, but Thorne beat him to it. ‘It’s a new TV show about a maverick, gay pathologist.’ He put a hand on Holland ’s shoulder, as if to introduce the star of the show. ‘You know the sort of thing. Fuzzy black-and-white bits, half a dozen serial killers in every episode…’

The clocks going back seemed to have brought the rush hour forward, and the North Circular was already starting to snarl up as Thorne nosed the car towards Finchley.

‘Things seem to be going well with DI Porter,’ Holland said. ‘It’s a few months now, isn’t it?’

Thorne searched Holland ’s face, but saw only honest curiosity. ‘Five, give or take a week. That’s a long time for me.’

‘It’s good…’

Thorne wasn’t about to argue. ‘How’s Chloe?’

Holland grinned. His daughter had turned three years old a couple of months earlier. ‘Can’t shut her up,’ he said. ‘Coming out with all sorts of weird shit. Stuff she’s picking up at nursery, whatever. She’s going a couple of days a week now. I told you that, didn’t I?’

It was the first Thorne had heard of it, but he nodded anyway.

‘Sophie’s trying to do some work part time, you know? That’ll be good for everyone, I reckon.’

‘Right…’

Holland had been nodding while he spoke. He carried on after he’d turned to look out of the window, as though he were trying to convince himself.

‘Definitely,’ Thorne said.

It was natural that he hadn’t seen quite so much of Holland outside the Job since Chloe had come along. But even when they spent time together at work, Thorne thought that he and Holland weren’t connecting in a way that perhaps they once had. He could see that his colleague – was he a colleague now, as opposed to a friend? – had a lot more on his plate since being made up to sergeant the year before, but Thorne wondered if it didn’t also have something to do with the more subtle demands of a family. With the grinding drive to become the sort of police officer Holland had once professed to despise: the head-down and shut-the-fuck-up kind of copper his father had been. The copper that sometimes, when he’d upset one too many of the wrong people, Thorne wished he had it in himself to be.

Pulling away from the lights at Henley ’s Corner, something beneath the BMW’s bonnet began to complain, and as Thorne wondered just how hard the complaint was going to hit his wallet, the jokes began. However uncertain things might be, however far they shifted, there would always be Holland ’s shtick about the car: the fact that it was yellow and almost as old as he was, and that Thorne could have bought a new one for what it cost him in repairs every year.

And it was all fair enough.

Coppers solved crimes or they didn’t. They laid down their lives to protect others and they shot innocent men for looking swarthy in the wrong place at the wrong time. But smart or stupid, honest or bent, they all took the piss. Took it, and had it taken.

And you didn’t need a psychology degree to figure out why.

Some were better at it than others. The likes of Andy Stone had a drawer stuffed with photocopies of colleagues’ warrant cards, so that when and if the time came, they could place embarrassing personal ads on their behalf in the back pages of The Job and Metropolitan Life. Bogus lonely-hearts stuff and requests for mail-order brides. When Samir Karim had split up with his wife a few years before, an ad had appeared the following week with his contact details offering: ‘Double bed for sale. Hardly used.’

Karim had laughed along with the rest of them, obviously.

‘Vorsprung, durch… utterly fucked,’ Holland said, getting into his stride.

Thorne steered the car slowly through the mess of traffic at the Brent Cross flyover, then turned north towards Hendon, waiting until Holland had hit him with his best shots.

‘Say what you like.’ Thorne stroked the steering wheel theatrically. ‘Still my baby.’

‘Listen to yourself,’ Holland said. ‘It’s a clapped-out piece of German scrap. It’s not Herbie…’

Thorne sighed and stared ahead, refusing to dignify the comment with a response. The blocks of single-storey warehouses and furniture superstores crawled by along the length of the A406: Carpet Express; Kingdom of Leather; Staples. His eye was caught by the Carphone Warehouse logo across a set of grey, metal shutters, and it suddenly struck Thorne that the reason for the killer’s delay in sending the photograph might have been altogether simpler yet more bizarre.

‘Fritz, maybe…’ Holland said.

Was it possible that, after committing the murder, the killer had kept a watch on Tucker’s flat? On seeing that the body was going undiscovered, had he simply decided to give the police a helping hand?

Ordered or disordered?

Perhaps he wanted someone to go to the trouble of finding out…

Next to him, Holland was saying something about a running joke that ran a damn sight better than the car did, but Thorne was already elsewhere. Thinking that the dead were never decorous. That death itself was rarely dignified, whether you were tottering towards collapse on a mixed ward or rotting into a carpet. But that for the most unfortunate, what was left could barely even be called ‘remains’.