Finally, a corner of her mouth turns upwards, and she nods in the direction of the TV.

‘Your ex-wife told me.’

This answer isn’t much better than her first, and makes just as little sense, until I see Anna appear on the screen. She’s standing outside the school, and reporting on the second victim, before I’ve even managed to get to the scene of the crime. There haven’t been any press statements yet; the only people who should know anything about a second murder at this stage could be counted on one hand.

‘I’ve got to go,’ I say again, before heading for the hall, and grabbing my jacket from the bannister where I always leave it. Something else I do that irritates my little sister. I reach for my Harry Potter scarf, but then decide to do without it.

‘Jack, wait up.’ Zoe follows me. ‘Be careful today, OK? Just because you used to be married, doesn’t mean that you should trust Anna.’

‘What does that mean?’

‘She’s more of a journalist than she was ever a wife, so watch what you say. And don’t… lose your temper with anyone.’

‘Why would I?’

She shrugs and I open the front door.

‘One more thing,’ she says, and I turn to face her, unable to hide my impatience.

‘What?’

‘Please don’t smoke in the house.’

I get in my car, feeling like a chastised child who has been caught out in more ways than one. I drive to the school I was parked outside only last night and, once again, it would appear that the entire Surrey police force has arrived before me.

There is only one TV sat truck here for now – Anna’s – but no sign of her or the BBC team, just an empty van. They must be taking a break. I looked up her cameraman on the system last night. It was unprofessional, but I was right to be suspicious. He’s got a record and a past I expect she knows nothing about.

Priya is waiting to meet me in the school reception, and hands me a coffee and a croissant. Her hair is tied up in a ponytail again, but her face looks different.

‘I’m not wearing my glasses,’ she says, as though reading my thoughts.

‘If you didn’t want to see another dead body so soon, you just had to say.’

‘I can see fine, thanks, sir. I thought I’d try contact lenses.’

Seems like an odd time to experiment, but women have always been a mystery to me.

‘Looks good,’ I say and she smiles. I instantly worry that I shouldn’t have said it – concerned that perhaps paying a female colleague a simple compliment somehow constitutes sexual harassment nowadays – so I take it back. ‘I meant the coffee,’ I add and take a sip.

Priya’s smile vanishes and I feel like an arsehole. I try to steer us towards a less personal subject.

‘Where did you find something that tastes this good, at this time, around here?’ I ask, holding up the cup.

‘It’s from Colombia.’

My response skips a beat.

‘That’s a long way to go.’

Her smile returns.

‘I made it for you at home before I left this morning, I thought you might need coffee. I have a whole thermos in the car, but I know how you like it in a paper cup – even though that is a little strange and bad for the environment – so I ordered some online. Paper cups, I mean. I just poured it when I saw you pulling in, so that it would be hot.’

I knew it. She’s in love with me. I might be middle-aged, but I’ve still got it. Not that anything can or will happen. I’ll let her down gently when the time is right. I take a bite of the croissant and it’s good. I decide not to ask where that came from; she probably baked it herself or had it flown in from France.

My phone rings, revealing my boss’s name, and I take longer than I should to answer it.

‘Good morning, sir.’

Kissing arse always leaves an unpleasant taste on my lips.

I listen while the weasel of a man tells me everything he thinks I’ve done wrong with the investigation, and bite my tongue so often I’m surprised it doesn’t have a hole. He’d never say it to my face. Firstly, I doubt he could find his way out of his office to do so, plus it’s hard for him to look down on me in person; I’m considerably taller. The man suffers from stunted growth as well as intellect, but I wait until he has said everything he wants to say, then tell him what he wants to hear. I find this is the fastest approach to get management off my back.

‘Yes, sir. Of course,’ I say, promising to keep him in the loop before hanging up.

Priya looks disappointed.

‘What?’ I ask.

She shrugs, but doesn’t answer. Her eyes judge me even if her words don’t. I think she overheard what the chief said:

‘This is a major fuck-up by the Major Crime Team on your watch.’

Myself and the entire MCT unit all worked eighteen hour-shifts yesterday. They’ve hardly slept, but something about what he said still stings. For some reason, on some level, it does feel as though all of this might be my fault.

‘Shall we?’ I ask Priya.

‘Yes, sir,’ she says, returning to her normal, efficient self. A version I’m much more comfortable with.

Priya leads the way through a warren of corridors. I ignore all the colourful posters on the walls, and focus instead on her lace-up shoes as they squeak along the polished floor. The black brogues – which oddly enough resemble school shoes to me – are considerably cleaner than yesterday in the muddy woods, so much so that I can’t help wondering whether they are a brand-new pair. Her ponytail swings from side to side as it always does, a hair-shaped pendulum, counting down as we get closer to victim number two. I am in no doubt that the murders are linked.

I keep a couple of steps behind Priya all the way, pretending to follow, but this is a building I am already surprisingly familiar with. I used to get dragged here by my parents all the time, to see my sister perform in school plays. Zoe was never top of her class academically – too much competition for that at a school like this – but she was a terrific actress. Still is. Perhaps it runs in the family. I can no longer pretend to myself that I wasn’t here last night, or that I didn’t see the light in the window of the office we are headed towards. If I had behaved differently then, this wouldn’t be happening now.

When we step into the room, the sight that greets us cannot fail to shock. It’s still pitch-black outside, but not in here. The bright police lights make the room seem like a film set, with the victim centre stage.

‘Can we cover up these windows, please, before the press start posting pictures online?’ I say, and several heads turn to stare in my direction.

There are a couple of uniformed officers I know, as well as some I don’t, and I’m pleased to see that Forensics have already arrived. It’s more or less the same target response team as yesterday, and they all seem a little shell-shocked. Looking at the crime scene, I don’t blame them.

‘I thought it was best to wait for you, sir,’ Priya says.

‘Fine, well I’m here now.’

The school office is more like a miniature library. Bookshelves line the back wall, and there is a huge framed map of the world on another. I see a glass cabinet full of trophies, and a large mahogany desk in the middle of the room. The headmistress is still sitting in her chair behind it, but her throat has been cut and her mouth is stretched into a scream.