When he eventually stalks onto the floor of the Bug House five minutes later, it seems to Seagram that Vos is in an even worse mood than before. Who the hell was the call from? she wonders. The tax man? What worries her is that any second now the boss’s black dog is going to start ripping out throats. As he heads across to the meeting room, she hurries across to intercept him.

‘Boss, the replacement is here,’ she says, careful not to say ‘the replacement for Entwistle’.

He stops and looks down at her. ‘Yes,’ he says. ‘I know.’

The meeting room is a cosy little annexe separated from the squad room by a partition wall. Its focal point is a large pull-down screen for the overhead projector, but as no one has ever figured out how the projector works in over ten years, the screen is used instead as an oversized memo board and is scarred with pinholes, Sellotape marks and crusts of Blu-tack from hundreds of different cases. Right now the board looks distinctly bare: a handful of assorted photographs from the scene, a map of the area around Stannington, a few desultory Post-it notes.

The squad is assembled and waiting.

‘I take it you’ve all met DC Ptolemy,’ Vos says, sweeping past them on his way to the board, and Ptolemy, who feels like the new girl in a classroom where everyone knows each other and, more importantly, knows the teacher, finds herself with a rictus smile on her face and wondering if she should wave or give a bow or just stand up and curtsey.

Instead she looks for help from Huggins and Fallow, with whom she has spent most of the morning, but they are just staring ahead with grim faces, as if they can sense teacher is in a bad mood. As for the other guy – Calvert? – he’s only just arrived himself and hasn’t made a sound, other than a dismissive grunt on his way to the nearest computer terminal. In fact, as she looks round the room, the only one who meets her gaze is the only other woman on the squad, Acting DS Seagram – and her nod of acknowledgement, while little more than a fractional tilt of the chin, seems like the most heart-warming welcome imaginable.

‘OK,’ Vos says. ‘So what we know is this: some time before 8.47 p.m. on Sunday night, Ahmed Doe is tied to a railway bridge by person or persons unknown. Prior to that, according to the pathologist, he was incapacitated with a stun gun. At 8.47 p.m. he is struck by the Newcastle to Edinburgh train. The body is catapulted into the neighbouring garden of our footballing friend, where it is discovered the next morning by the gardener. As yet we have no name for the victim, and his only distinguishing feature is a distinctive tattoo or branding mark on his testicles. Any questions? John?’

‘The branding mark,’ Fallow says. ‘Are we thinking torture?’

‘I’m more inclined to go with gang initiation. Mayson, do a trawl of the international databases. See if there’s any mention of this KK design.’

‘You think our guy is foreign?’ Huggins says. ‘I mean he looks foreign, but—’

‘I don’t think anything, Phil. I’m relying on you people to tell me. And unless he was a masochist escapologist who got it wrong, we are treating this as murder. I take it you’ve worked a murder case before?’

It takes a moment for Ptolemy to realize that Vos is talking to her.

‘Yes, sir.’

Ptolemy wonders if Vos has read her file. Her one and only murder case as a detective was a domestic disagreement that got out of hand in a remote cottage in the Cheviots. A farm hand had returned home at the end of a two-day bender and taken exception to his wife’s nagging, killing her with a single punch. He had then called the police and had been sitting in his kitchen, waiting, when Ptolemy and the uniformed response unit arrived an hour later.

‘So what do you think?’

She clears her throat. ‘I was . . . thinking about motive, sir?’

‘Go on.’

‘Well, the nature of the victim’s death suggests to me one of two things: either the killer was teaching him a lesson, or he was sending a message.’

To her surprise, Vos nods at Seagram, who writes the two words ‘LESSON’ and ‘MESSAGE’ on the board in black felt-tip.

‘OK,’ he says. ‘What do we think about that?’

‘Either way it’s been carried out with extreme prejudice,’ Huggins says.

‘It’s got to be gang-related,’ Fallow says.

And then everybody is speculating at once, leaving Ptolemy not knowing what to say.

Eventually Vos calls order. ‘Right,’ he says. ‘I think we all know what needs to be done. Let’s get to work.’ Then he looks at Ptolemy. ‘Come with me,’ he says. ‘There’s someone I want you to meet.’

Vos’s car is parked in the staff car park at the rear of the building. By the time Ptolemy has finished buckling her seatbelt, Vos has already swung the vehicle into the traffic streaming west out of the city.

‘So what do you think?’ he says.

‘Of the team? They’re nice. I like them.’

‘No doubt Huggins and Fallow have already invited you out for a drink.’

She smiles. ‘Phil did suggest it would be a good idea to bond.’

‘What did you say?’

‘Maybe another time.’

‘Wise move,’ Vos says. ‘Huggins has still got one foot in the sixth-form common room. Fallow is just easily led astray. You go drinking with them, you’ll end up at two in the morning in a lap-dancing bar on the Quayside.’

‘I thought DC Fallow was married, sir.’

‘He is,’ Vos says.

‘DC Calvert seems a little . . .’

‘Odd? He is. Sometimes I don’t understand a word he says. But he’s harmless. And if you ever want your house rewiring, he’s your man. But if you have any problems, see Bernice Seagram. Or Una Cattrall. In fact, just see Una. She runs the department.’

They head down the hill, past the municipal crematorium and out beyond the Western Bypass to the A69 dual carriageway that connects the city to the market towns and villages of the Tyne Valley commuter belt.

‘Detective Superintendent Anderson thinks a great deal of you,’ Vos says. ‘She tells me you were hand-picked to join my squad.’

‘It was a surprise,’ Ptolemy admits. ‘I didn’t even know I was on a shortlist.’

‘You could have said no.’

‘You don’t say no to a detective superintendent, sir.’

Ptolemy sees a half-smile on Vos’s face.

‘Good answer, Ptolemy,’ he says. ‘You’ll go far.’

They’re out beyond the city now. Though it’s only six o’clock, ahead of them the sun is already starting to sink with the depressing inevitability of early autumn.

‘You could have said no, sir,’ she says.

‘No to what?’

‘To me joining your squad. I assume you’ve read my file. I’m not very experienced.’

‘I haven’t read your file, Ptolemy,’ Vos says. ‘And I don’t intend to.’

He indicates left and turns onto the slip road marked Heddon-on-the-Wall. Soon they come to a pub called the Three Tuns, positioned on a crossroads. Vos swings into the car park and he and Ptolemy go inside. It’s the calm before early doors; just a handful of regulars at the bar. Vos buys a pint of bitter and a lime and soda and then leads Ptolemy into a quiet corner, away from the inevitable TV screen.

‘Can I ask you something, sir?’ Ptolemy says.

‘Sure.’

‘What do you think happened? To the victim.’

Vos says nothing for a while. ‘To be honest, I don’t know what to think,’ he says presently. ‘But I will soon enough.’

‘Well, thanks for including me,’ Ptolemy says. ‘I won’t let you down.’

‘I’m not including you, Ptolemy.’

‘I don’t understand, sir.’

‘There’s more to Major Crime than murder investigations. There’s something else I want you to do for me.’

The main door opens and a man comes in. He is skinny, with unkempt dark hair and a couple of days’ growth on his pale face. He is wearing drainpipe jeans and a battered biker jacket. He orders a pint of lager and a bag of crisps and then, to Ptolemy’s surprise, comes over to where they are sitting and pulls up a stool.