‘I just wanted to stress that everything we talked about the other day remains confidential,’ Nunn said.

‘Go on then.’

Nunn smiled, but only with his mouth.

‘It seems a bit bloody odd,’ Thorne said, ‘that you should be so adamant about it. Considering Skinner’s dead, I mean.’

‘Nothing’s changed.’

‘Try telling that to Mrs Skinner.’

‘Things don’t just stop, that’s all I’m saying.’

‘“T”s to cross and “i”s to dot, right?’

‘Little things like whether Mrs Skinner gets her husband’s police pension if it turns out there would have been sufficient evidence to press charges against him.’

Thorne almost laughed for the first time in a day or more. ‘Is that what this is all about?’

‘I’m just making a point. This has got to run its course.’

‘Look, I know you lot love all this cloak-and-dagger shit,’ Thorne said. ‘But the fact that Skinner may not have been completely kosher has probably got quite a lot to do with why he’s dead. Why several people are dead. So it’s not like we can keep this a secret. I’ve already spoken to my DCI about it. It’s part of our case.’

Nunn looked up at the information board; thinking about it. ‘As long as you really try to keep out of our way,’ he said.

They didn’t have to wait long for a southbound train, and Thorne was grateful. Standing on the platform was conducive to nothing more than small talk and he was fresh out of it. The train was more or less empty: they had a carriage to themselves. It was surprisingly hot once the doors had shut and they were moving, and Nunn stood to take off his coat; folded it across his knees.

‘Is that really true?’ Thorne asked. ‘That nothing’s changed?’ He was desperate to know exactly what Nunn had meant. Was the status of the investigation still active for such prosaic reasons as Nunn had suggested, or was there something else going on? Were they actively pursuing a second officer?

‘Nothing substantial,’ Nunn said.

‘Well, thanks for sorting that one out for me.’ Thorne wondered if DPS recruits did courses in remaining amicably non-committal. If they shared classroom space with politicians and certain women he’d been involved with. ‘Good result, or bad?’ he asked.

‘What?’

‘Skinner being murdered.’

‘Hang on a minute…’

‘I’m serious. We both know Skinner was as bent as a nine-bob note, even though nobody’s come out and said it, so what do the powers-that-be make of his getting knocked off? Are they happy enough to be rid of a corrupt officer without having to go to the trouble of actually doing it themselves? Saves embarrassment, I would have thought.’

‘Nobody’s embarrassed.’

‘And what about you? You’ve lost the chance to nick him. Don’t you feel a bit… robbed?’

‘More than a bit,’ Nunn said, enjoying how much his answer took Thorne aback. ‘That’s a shock, right? Don’t you think that getting shot of a seriously corrupt officer is every bit as rewarding as catching a killer, or a gang of armed robbers, or nicking a drug dealer? I’ve done all those things, and I can promise you that it is. Every bit.’

Thorne could only shrug, but he wasn’t sure he believed Nunn. At least, he wasn’t certain he would feel the same way; would get the same satisfaction from nabbing a bent copper as he would from catching a murderer.

Until he remembered they could be one and the same thing.

There wasn’t too much conversation from then on. People joined the train at Brent Cross and Golders Green, and it was full by the time they pulled away from Hampstead. Thorne and Nunn had been raising their voices to be heard above the noise of the train, but with passengers sitting around and standing above them, lurching as the train rocked and juddered, neither man was very keen to talk any more.

‘This is me,’ Thorne said as the train approached Camden.

Nunn had been sitting on the flap of Thorne’s jacket, shifted slightly to let him stand up. ‘You know where I am if anything else comes up.’

‘Right. Same here, for what it’s worth.’

Nunn looked at his watch. ‘I don’t suppose you fancy a quick drink?’

The invitation seemed genuine enough and it took Thorne completely by surprise. He looked at his own watch while he thought about what to say, but Nunn’s expression as he’d asked the question had revealed a thumbnail snap of the man that he hadn’t expected to see. That was sad, for all manner of reasons.

Copper. Lives alone. Doesn’t mix too well with others…

‘Sounds like a great idea,’ Thorne said. ‘But my girlfriend’s cooking me dinner…’

The Bengal Lancer’s home delivery was as reliable as always, and the two of them made short work of rogan gosht and chicken tikka, with mutter paneer and a sag bhaji, pilau rice and nan bread. Thorne fetched two more bottles of Kingfisher from the fridge, then carried the plates out to the kitchen.

He shouted through to the living room: ‘I meant to say, about my mobile…’

Louise called back, asked him to say it again. His words had been lost in noise from the TV as she flicked through the channels.

Thorne came to the doorway and Louise turned down the volume. ‘Just about my mobile,’ he said. ‘It’s nothing important, but you need to call me on the prepay phone from now on.’

‘I thought you had your old Nokia back.’

‘I do, but that line is being… monitored. You know, in case Brooks sends another message, in case he decides to call, whatever. So best if you use the prepay. You’ve got the number, right?’

She told him that she had. He said he could go to prison for what he’d just told her. She promised to visit.

‘You think he might, then? Get in touch again?’

‘God knows.’

‘I presume they’ve set up a trace on it, right? Silly fucker rings, you’ve got him. Simple as that.’

‘Yeah, be nice,’ Thorne said. He drifted back into the kitchen and Louise turned the sound back up on the TV. He finished loading the dishwasher then leaned back against the draining board. From where he was standing he could see her in the living room. She had found some cable channel showing eighties music videos and began humming along with an old Depeche Mode track.

Thorne glanced over at his leather jacket, hung across the back of a kitchen chair. His Nokia was in one of the inside pockets; the prepay phone was in the other. He’d programmed distinctive ringtones into each, so there would be no confusion.

He polished off his beer and started an argument with himself.

He’d been straight with Louise about the phone being monitored when she didn’t strictly need to know, hadn’t he? So, maybe that excused his not telling her about the message he’d sent to Marcus Brooks. Or went some way towards excusing it, at least. Wasn’t she better off not knowing about it? Not being involved? Not getting dragged through the steaming trail of shit he was busy creating?

He knew she wouldn’t buy that for a minute.

It came from the same well-worn bag of tricks as, ‘I didn’t tell you I was sleeping with someone else because I knew you’d be upset, and I didn’t want to hurt you’. Thorne knew, deep down, that it had more to do with cowardice than it did with compassion. That the lie by omission was usually worse in the long run than the terrible truth.

He still wasn’t going to tell her, though. Not if he could avoid it…

When Thorne went back into the living room, they made themselves comfortable. They sat together on the floor in front of the sofa; broke up the last of the poppadoms and watched Yvonne Kitson do her turn on Crimewatch.

In a five-minute round-up slot at the end of the programme, Kitson fronted an appeal for more information about the murder of Deniz Sedat. Wearing a well-chosen, charcoal business suit, she said that the incident had ‘shocked a community’ and urged anyone with information to get in touch. Assured them that calls would be treated in confidence. She finished with a special plea to the young woman who had called once already; who had seemed eager to tell them something and whom they were extremely keen to talk to again.