Thorne stuck his hand out for the piece of paper.

‘They’re getting a proper scan organised,’ Karim said, handing it over. ‘They’ll email that across in an hour or so, but meantime they said they’d fax over what they’ve got already and we can call if we’ve got any questions.’

Thorne grunted a ‘thanks’ as he squeezed past Karim into the corridor, then turned towards the Incident Room. A minute later, when he had reached the corner of the room where the fax machine sat, he called the FSS lab in Victoria and asked for the doctor whose name Karim had scribbled down.

‘Bloody hell, that was fast, I haven’t even sent it yet.’ Doctor Clive Kelly asked Thorne to hold on. After a rustle of papers and some slightly tetchy muttering Thorne heard a series of tell-tale beeps. Then the doctor came back on the line: ‘Right, it’s on the way.’

‘I’m standing over the fax machine,’ Thorne said.

‘Not that I could tell you where it is while it’s on the way,’ Kelly said. ‘These things are a mystery to me.’

The fax machine hummed into life and a sheet of paper started to appear. ‘You’re supposed to be the scientist,’ Thorne said.

Kelly laughed. ‘Not my speciality,’ he said. ‘You give me a document and I’ll tell you where the paper came from and when the ink was produced and, if I’m having a good day, I might even tell you how many times the bloke who wrote it scratched his arse. But me putting that document on a machine and pressing a button and you taking it out of another machine in a room miles away… that’s just bloody witchcraft.’

As soon as the fax had been received, Thorne took the sheet from the tray and stared down at the new and extended sequence of letters and numbers:

VEY48

ADD597-86/09

SYMPHONY

Said, ‘What am I looking at?’

‘Let’s start at the bottom,’ Kelly said. ‘That’s the easy bit. “Symphony” is just a type of MRI scanner. It’s basically the name of the machine that did the X-ray. It’s not strictly speaking an X-ray, of course, as it uses magnetic resonance as opposed to radiation, but-’

‘X-ray of what?’

‘Still can’t tell you that, I’m afraid. But we know where it was done. See the second line?’

‘I’m looking…’

‘We thought the numbers might be some Health Service reference or other, and it turns out to be the area code for Cambridge University Hospitals NHS Trust. And the three letters – ADD – that’s the hospital itself.’ Kelly waited, as though expecting Thorne to start guessing.

‘Right…?’

‘Addenbrooke’s.’

‘In Cambridge?’

‘Easy when you know the answer, isn’t it? There isn’t too much more we can tell you, I’m afraid.’

Thorne said it was OK, that he didn’t really need any more. At forty or so miles away, it was not the nearest hospital to Her Majesty’s Prison Whitemoor, but Addenbrooke’s had a worldwide reputation when it came to neurosurgery. Now Thorne knew exactly what kind of X-ray the pieces of plastic had been cut from.

‘That first line’s still got us all racking our brains,’ Kelly said.

VEY48

Thorne thanked Kelly for his help, then said, ‘I think “ 48” is probably the age of the patient when the X-ray was done.’

‘Easy when you know the answer.’

‘And “VEY” are the last three letters of his name.’

Sally puts down the phone for the third time that day and walks slowly back to her armchair. Buzz is asleep in front of the gas fire, twitching like he’s dreaming of chasing cats or something, and she has to step across him to get to the chair. She reaches down to tug at his soft brown ears, which he loves, before she sits down.

She’s been ringing every day since it happened, trying to get some information. ‘Wasting my time,’ she told her friend Betty. ‘Nobody wants to tell me anything.’ She talked to the police on several occasions in the days immediately afterwards and gave a full statement in the end, but now they speak to her as though she were annoying them. Like they have far better things to do, which always makes her laugh.

It wasn’t like she was asking for anything they weren’t allowed to tell her, not as far as she knows. She just wants to know what’s happening. If there is going to be a court case of some sort, because somebody has to be to blamed for what happened, surely?

They just fobbed her off. Trotted out the same old line about enquiries being ongoing. She could almost hear the sigh in the voice of whichever policeman happened to be manning the phones that day.

‘Oh Christ, it’s that silly old woman from the park again…’

A car door slams somewhere outside and Buzz is up, tearing across to the door, barking while she flicks through the TV channels and tells him not to be so silly. Afterwards, he comes back and lays his head on her leg, his tail going ten to the dozen.

‘I know,’ she says. ‘I’m sorry, Buzzy-Boy. Not just yet, eh?’

The dog is getting fatter, she can see that, and it’s her fault. She hasn’t been out of the house since it happened, and Betty can’t walk him, not with her legs. Sally’s daughter has taken him out a couple of times, but Buzz misses the daily visit to the park. They both miss it.

She’s got as far as the front gate a couple of times, but her legs have started to tremble and she’s had to go back inside.

‘It’s hardly surprising,’ Betty says. ‘It’s a hell of a shock, getting caught up in something like that.’

But Betty’s wrong. It isn’t shock. It’s guilt.

The woman had been in a hurry, that was obvious, hadn’t wanted to hang about and chat, but Sally thought there must have been something she could have done to keep them there. If she had only talked to the boy for a bit longer, just a few minutes would have done it. Got him to throw a stick for Buzz, maybe. At the time she’d thought he was quiet, that was all. It wasn’t until she read the papers afterwards that she’d found out there was anything wrong with him.

Lord, just thinking about that poor boy keeps her awake most of the night.

The stupidest thing of all was, a few minutes after she’d watched the pair of them hurry away, that policeman’s identification card was being waved in her face and she’d been jabbering away ten to the dozen like the silly old cow she was. Telling him he’d just missed them and showing him which way they’d gone.

She should have known something wasn’t right as soon as he started running.

Sally gets up and goes to the kitchen, makes herself some tea and takes a packet of digestives from the cupboard. She brings them back to the chair on a small tray that Betty picked up for her in Southend, looks through the TV listings magazine to see if there’s one of her quiz shows on.

She’ll try to take Buzz out tomorrow, she tells herself, or failing that the next day. The weather forecast isn’t too good anyway.

She settles down in her chair. Watches an old episode of Catchphrase and drinks her tea. She can still feel it in her legs and in her chest, and the tremor in her hand makes the cup shake a little against the saucer.