As I struggled in the glue of the file, Mercer was performing a similar task with the ongoing operation. The rest of the team were either out in the field or working from offices in other parts of the building, and since the briefing it had just been the two of us here. Conversation hadn't flowed, but we were both busy. Members of the team logged in as necessary to bring reports and updates, and when he wasn't discussing things with them Mercer maintained the same pose: head bowed, poring over paperwork, co-ordinating everything from the confines of his own head. When he wasn't making calls, he was taking them; when he wasn't doing that, he was reading through piles of documents or chasing others. He didn't get up from his seat, but every time I looked at him I saw a flurry of internal activity.
Among it all, there were regular phone calls to his superior, Detective Inspector Alan White, informing him of developments as they occurred. Mercer always seemed eager to get rid of him. I didn't know whether he disliked having to answer to someone else about his own case, but whatever the explanation he constantly downplayed its importance - to the degree that I began to really notice it. Not once did he refer to the 50/50 Killer. Instead, he focused on the minutiae of the case, and I thought it was strange, given his insistence on how obvious the connection was.
What little progress there was came in dribs and drabs. Simon phoned in from the crime lab. Two sets of prints had been found in the house. One belonged to Kevin Simpson; the other was unknown. Although it was possible the killer had left us a gift, it was more likely the second prints belonged to Jodie. And we were no closer to discovering who she was.
Pete had been talking to Simpson's ex-girlfriends, sending a report in after each. I watched a little blankly as one after another was crossed off the list of possibles. My own door-to-door team were similarly prolific; the results equally unhelpful. Previous gaps in the record had been filled and the interviews had moved on to the surrounding streets, but no new leads had emerged as a result.
I watched Mercer the whole time, quietly astonished by the way he was handling things. He seemed to hold everything in his head at once, staring intently at the screen during each report, nodding to himself. His expression occasionally became blank and faraway as he slotted each new fact into place. For me, it was hard enough playing catch-up on the file, never mind how it was continuing to grow. At least I had a framework to rethink the crime scene at Kevin Simpson's house. Although the signature and the game were key, Greg was right that the scene this morning was different. Whoever this Jodie was, she hadn't been involved in the same way previous victims were.
It's been two years. He's been planning.
I wondered at the picture Mercer was working with, but for now that was his concern. Our job was to gather the small amounts of evidence that were available; his was to make sense of them.
And so it continued.
A little before six, Greg videophoned with an IT report. There was bad news. If there had been any reference to Jodie or Scott on Simpson's PC, whether in email, contacts or a random document, the killer had erased it. As Greg had told us earlier, we wouldn't find their identities from the computer.
'However, we do have a major victory,' he said.
His tone was a little off, but Mercer had no time for the sarcasm.
'Go on.'
Greg sent the clips through. There were six: grainy CCTV stills of the main road near Simpson's house. Six different white vans. You couldn't read the number plates in these images but IT had enhanced them and managed to secure identification of all six.
'These were all taken this morning, around the time the killer would have been leaving.' Greg was absently scratching his sideburns. 'It goes without saying, there are a lot of white vans around at that time of day.'
'But you said it anyway, Greg. Well done. Names and addresses?'
'On their way over now.'
Mercer turned to me: 'Your door-to-door team?'
'Still working the streets around Simpson's house. With ever-decreasing returns.'
'Pull them and get them on this instead. Greg's right that it's probably nothing, but you never know.'
'Okay.'
'Full video and audio.'
There it was again. I found myself gritting my teeth, then told myself it was just his way and contacted my team, setting about the transfer of the names and addresses I needed them to investigate. I deliberately repeated Mercer's instructions - a little archly myself - but his attention was elsewhere: he was dialling a number, presumably to let White know about this latest development.
His expression was unreadable. Looking at him, I thought, was like trying to watch a battleground from above the clouds.
After talking to the door team, I returned my attention to the file. There was a large section towards the end I'd yet to read, and it was about to provide me with more insight into the day's events than was entirely comfortable. This part was about Detective Andrew Dyson.
A father of two, Dyson had been working on Mercer's team for over ten years. I had listened to him interviewing Daniel Roseneil, who had told him all about the Devil. A year after, Dyson met that Devil in the flesh, in the process becoming the last known victim of the 50/50 Killer.
Now, two years later, I was sitting at what had once been his desk, watching footage from the day it occurred.
The film had been taken by a CCTV camera on a lamp-post in a quiet suburban street. It was angled badly but gave a reasonable view of the road. Perhaps fifty metres from the lens, I saw Dyson. He had parked outside an ordinary semi-detached house and was walking up to the front door. The clock in the corner of the screen said it was two thirteen in the afternoon.
These were Dyson's final moments: the last time he'd been seen alive. In this case, the seeing had been done by a digital storage unit, which was colder and more clinical than an actual witness, and made him seem even more vulnerable. On screen, he was already a lonely figure: his hands in his pockets, coat pulled tight round him against the cold. I wanted to reach out and warn him, but I was watching a ghost and all I could do was reach out for coffee. And watch as the last moments of his finished history repeated themselves.
It had been three months since the Clarks were attacked, and in that time the investigation had hit a wall. There was so little in the way of forensic evidence to go on, and the handful of leads had petered out or been exhausted. Mercer's resources were being steadily depleted; his men allocated to newer, more pressing assignments. For now, the team itself wasn't giving up - or at least Mercer wasn't. They were going over every fact they had: reinterviewing friends, family and neighbours; chasing the edges of gaps and gaining extra detail where they could.
I knew what it was like to be involved in the late stages of an investigation that was going nowhere: there was an inevitability to it. You knew you'd failed, but you kept going anyway, hoping for some kind of break. But never this kind.
The house Dyson was visiting was as flat and square as the pale red bricks it was made from; it looked like it had been built as a bodyguard for the more expensive properties in the distance. There was a long, straight driveway down one side, ending in a dark garage. Two bins, a black one for rubbish, a green for recycling. The garden out front was generally neat, but it had been left untended through the winter months. I could see the bushes trembling slightly in the wind. Behind all this, the sky was dark grey and mottled. Ominous. Along with the space between properties, the sky made the entire street look like a row of drab gravestones, frozen and weathered away in some cliff-top cemetery.
Dyson had rung the bell. Now, he was shuffling in the cold. He seemed too small, dwarfed by the house, as though it might swallow him whole.
Come on, come on,
I thought.
He rubbed his hands together.
It's freezing out here.
He glanced up and down the street before leaning on the doorbell again.
The surveillance equipment the killer used was expensive and specialised, but there were at least two shops in the city that sold it, along with numerous sites where it could be bought online. By their very nature, the places that did stock it weren't keen on co-operating with the police, but under pressure they had. Lists of security experts, jealous husbands and assorted oddballs had been checked, the suspects on each list eliminated one by one.
That day, Dyson was going over old ground, revisiting the home of Frank Walker, a man who'd bought a couple of listening devices a few years before. He'd already been interviewed without any problem: no flags, no concerns. This visit was just a formality, so the day should have been a non-event. Dyson had no reason to think he might be in any danger. The file speculated this was why he hadn't turned on his recording equipment yet.
When I came to that, I forced myself to reread it. But there it was: one single lapse in concentration, brought on presumably by boredom or repetition. A lack of alertness. If he'd been more on guard, perhaps things might have turned out differently. The audio of his attack would have been relayed from the clip at his belt to the receiver in the car, and from there to the department. He might have lived.
I glanced across at Mercer. He was buried in the reports and didn't notice me looking, but I saw him in a slightly new light. Earlier, I'd resented his insistence on full video, full audio in the interviews. In a way I still did, but at least now I understood the reasons behind it.
On the computer screen, the clock in the corner ticked away the seconds. A full fifteen elapsed before Dyson reached out and pushed the door. It must have been slightly ajar because it opened inwards at the pressure. He leaned inside, his hand on the doorframe. I imagined him shouting,
'
Hello? It's the police.
Anyone in?
'
He hovered for a moment, and I felt my heart flutter. This was the moment. The exact truth about what happened after this would remain lost to us until we caught the man who'd lived there, the man who had been hiding within. Even then we might never know why Dyson decided to go inside. One theory was that he must have seen something in the kitchen that disturbed him enough to enter; another, that he heard a noise - a fake call for help, perhaps. Whatever the explanation, within seconds of opening the door he had entered the kitchen and disappeared.
The next camera to record him would belong to a crime-scene technician.
I kept watching, anyway. Whoever had compiled the footage had included an extra ten seconds at the end showing nothing but the still house and its quivering garden. It was possibly out of respect, but I found myself thinking about what was happening inside, out of sight, and I was glad when it cut off.
Returning to the main report, I read that Dyson's body had been found three hours later, after he'd failed to check in and not responded to calls. It was all too easy to imagine the unanswered crackle echoing around the empty living room they eventually found him in; his location had been traced from the car parked outside.
The house belonging to 'Frank Walker' turned out to be empty. The floorboards and walls were bare, and there was nothing in the way of furniture apart from a desk by the phone line and a mattress upstairs. Even though the place had been rented by Walker for several years, it was obvious that nobody had lived there for any length of time. Frank Walker was a fiction, a cleverly engineered fraud with an elaborate but false history laid out behind him, as empty and hollow as the house itself. The 50/50 Killer had invented him as a ghost identity. Both the name and the accommodation were just bolt-holes to him.
I pictured the killer flitting between the nests he'd made throughout the city, shedding identities the way a spider discards its skin. The house in the film was a little pocket of rank air, bubbled up to the surface of our world. It had been discovered, so he had moved on to another.
Nests. It made him seem even more of a monster.
Andrew Dyson was found lying on the floor in the living room, curled on his side, hugging the puncture wounds in his stomach. The killer had calmly attacked him with two long, thin-bladed knives, stabbing him six times: methodical and calculated. The cuts were clean and deep, in two bunches: front and side. There were no further injuries. Dyson had died slowly, of shock and blood loss, while his murderer moved around the house and cleaned any remaining evidence carefully away, room by room.
By the time the police arrived, he was long gone: disappeared out the back, apparently on foot. No vehicle had ever been registered to him. Nobody knew him. His bank account contained several thousand pounds, but the transactions were muddied and impossible to trace. No further attempt at withdrawal was ever made. He dumped the money as easily as the identity.
Frank Walker simply vanished, leaving Dyson's corpse behind: one last victim, like a husk in a web.
There was more to the file after that but, like the CCTV footage, it carried on for a few faltering moments that were ultimately unnecessary. Greg had completed a full dissection of the Frank Walker identity, exploring all the possible leads before coming to a halt at each dead end. Walker's house was stripped down practically to its foundations, but proved as clean of forensic evidence as any of the killer's primary crime scenes. His neighbours were all interviewed. None of them had ever seen him.
Nothing came of any of it.
As I finished, though, I found I was more concerned by what wasn't in the file. The team had maintained authority for the investigation after Dyson's death, but John Mercer's name was almost immediately conspicuous by its absence. The case had been placed back under the overall control of Detective Sergeant Geoff Hunter.
I broke off from the file and looked over at Mercer.
He was still in that familiar pose: elbows on the desk, fingers now splayed over his downturned face, lifting his hair up at the front. Still deeply involved in the papers and reports he was wrestling with.