Back at the office there were still a few Anthony Garveys to trace and eliminate. There was paperwork for the DVLA and assorted credit-reference agencies to be completed as part of the hunt for Graham Fowler and Simon Walsh; liaison with forces in the north in an effort to track down Andrew Dowd. So, in terms of excitement, there was nothing to match the small wager that Thorne and Kitson had made with each other on the way back from Whetstone.

‘By the end of the day, I reckon,’ Kitson had said.

‘No chance.’

‘I’m telling you. Collins is the type who likes to have her say.’

There was every chance Kitson was right, but Thorne was in the mood to argue that white was black. ‘Tomorrow,’ he’d said. ‘Earliest, if at all.’

‘Tenner?’

Being of a mind to argue – ‘chopsy’, his father used to call it – was one thing, but this was cold, hard cash. Thorne had read somewhere that the buzz of gambling lay in the fear of losing far more than in the possibility of winning, and having recently kicked an online poker habit, he’d been looking for something to make his heart beat a little bit faster. ‘You’re on,’ he’d said.

With fifteen minutes until going-home time, Sam Karim put his head round the door to say that Brigstocke wanted a word, and Thorne’s heart-rate increased for all the wrong reasons. ‘How are you going to spend the money?’ he asked on his way to the door.

‘I’m saving up for shoes,’ Kitson said. ‘Do you want to go double or quits?’

‘On what?’

‘Another tenner says Spurs lose tomorrow.’

At home against Aston Villa. Should be guaranteed at least a point. It was Spurs, though…

‘I think somebody’s bottle’s gone,’ Kitson said.

Karim was still standing in the doorway. ‘The guv’nor did say now.’

‘Stick it up your arse,’ Thorne said. ‘Both of you.’

‘I think maybe you should make another appointment to see that brain doctor,’ Brigstocke said. He leaned back against the edge of his desk, arms folded.

Thorne said nothing. It was usually best just to sit there and take it.

‘Tell him to have a look, see if he can find one.’

Brigstocke had moved on from the straightforward, high-volume bollocking – he had done that while recounting his fifteen-minute phone conversation with Nina Collins – and was now on to the sarcasm. Before long he would be into the last phase, which Thorne enjoyed the least: the one where the pitch dropped and the tone became one of sadness and disappointment, as though the offence for which he was dishing out the dressing down had actually wounded him. Thorne knew that Brigstocke had learned this ‘you’ve let me down, you’ve let yourself down, you’ve let the whole school down’ approach from Trevor Jesmond, who considered himself a master of it. Thorne had been on the receiving end many times, had looked suitably chastened at the slowly shaking head and the puppy-in-need-of-a-home expression, but in Jesmond’s case he always relished it, working on the principle that if he was upsetting the superintendent, he was clearly doing something right.

‘Mitchell was terrified,’ Brigstocke said. ‘Poor woman’s shitting herself, according to her friend.’

‘That was the idea.’

‘Oh, thank Christ for that. There I was thinking you were showing her confidential photographs of all the murder victims because you were an insensitive idiot who was gagging to get back into uniform. Have you still got a pointed hat?’

‘Not all the victims,’ Thorne said.

‘What?’

‘It wasn’t all the victims. Just the Mackens.’

‘Well, that’s OK then.’

Thorne couldn’t prevent the faintest of smirks washing across his face. ‘Just a sample.’

‘Jesus, Tom…’

‘Did it work?’

Brigstocke stared at him for a few seconds, as though toying with one last cathartic bout of shouting, before walking behind his desk and sitting down. ‘Debbie Mitchell’s moving in with Nina Collins,’ he said. ‘It’s only a couple of streets away-’

‘Doesn’t matter, as long as she moves.’

‘She wants to stay close to the park, she says. It’s the kid’s favourite place, apparently.’

‘Well, she can forget about that for a while.’

‘Plus, the kid knows Nina, so there shouldn’t be too much disruption. I understand he doesn’t respond well to… upheaval.’

Thorne told Brigstocke he was right. He remembered the boy’s smile, how easily it appeared and how astounding it was, considering that upheaval was something he had lived with for a long time. ‘So, I’m not in the shit then?’

It was Brigstocke’s turn to smirk. ‘Oh, don’t worry, if Collins or Mitchell decides to make any sort of official complaint, I’ll give you up like a shot.’

‘You’re a pal,’ Thorne said.

‘Yes, I am.’ Brigstocke looked down to the papers on his desk, as though he were good and ready for Thorne to leave. ‘Or I would have given you up already.’

Thorne recognised a cue and turned for the door, but Brigstocke called him back.

‘You were wrong about Anthony Garvey,’ he said.

‘Yeah?’

‘Don’t know about the name, but we can be pretty sure he’s Raymond Garvey’s son.’

Thorne nodded. ‘The DNA…’

‘We had Garvey senior’s on file, obviously, so we ran a match with the sample we got from under Catherine Burke’s fingernails. We can be ninety-nine per cent sure they’re father and son.’

‘Ninety-nine per cent?’

Brigstocke knew that Thorne understood why they could not declare it a 100 per cent match, but he said it anyway, enjoying the moment. ‘To be certain, we need to know who the mother was.’ The look, before Brigstocke dropped his eyes back to his paperwork, said, ‘Now we’re done.’

Walking out into the car-park, Kitson – ten pounds richer – said, ‘You remember the argument with Brigstocke in the pub? That stuff about the “tension” between the need to catch the killer and the need to protect the potential victims.’

‘I think that’s when his bad mood started,’ Thorne said. ‘That, or the fact that I got the last lamb casserole.’

‘Seriously.’

‘What?’

‘I was thinking. Didn’t it seem like nobody was trying very hard to get Debbie Mitchell out of that house?’

‘Well, she certainly took some shifting.’

‘You managed it, though. How come nobody else did?’

It was cold and starting to rain. They waited under the concrete overhang outside the rear entrance to Becke House, Thorne’s car fifty yards to his left and Kitson’s further away in the other direction.

‘You saying they were happy to let her stay there as some kind of bait?’ Thorne asked.

‘Well, it wasn’t like they had to plan it or anything. I mean, she didn’t want to leave, so maybe someone thought, Let’s use this to our advantage.’

‘Then we can’t be blamed if it all goes tits up.’

‘Right,’ Kitson said. ‘They stick a few unmarked cars around the place, set up an observation point, cameras, whatever.’

Thorne was nodding, going with it. ‘And the brass are pissed off with me, not because of this business with the crime-scene photos, but because they had their next victim sitting there waiting for the killer on a plate, and I went and ballsed it up.’

‘Maybe.’ Kitson was wearing a grey hooded top under a leather jacket. She raised the hood, stared out into the drizzle. ‘I’m just thinking out loud. It’s been a long day.’

‘You’ve had sillier ideas,’ Thorne said.

‘You think so?’

‘For sure.’ Thorne turned to her and held the look to let her know that he meant it, before allowing the smile to come. ‘We’re definitely worth a point against Villa tomorrow.’

‘You should have taken the bet then,’ Kitson said.

The alert tone on Thorne’s mobile sounded. He fished the handset from his pocket. The text was from Louise: celebration drink with team after work. won’t be 2 late. X.