Ten more minutes of conversation with Jacques left Stacey more convinced than ever that she was on to something and had several new avenues of inquiry to pursue. Although no useful forensic evidence had been recovered from any of the bodies, Jacques suggested she review the autopsy reports to see if any aspects of the killings supported the existence of a female suspect.

Another tiny smile crept across Stacey’s lips. She could feel that rising ball of excitement that manifested itself whenever she came close to solving a case, and she was certain that she was now on the final straight for this one. She picked the phone up once more and immediately dialled a number from memory, a number she had called dozens of times before over the years.

Not only would this call give her the chance to qualify her theory further, it would also be an opportunity to share what could be a key development with one of the few people she considered to be a friend. After half a dozen rings the call connected and a familiar voice sounded through the earpiece.

‘This is Dr Jessica Matthews. Sorry I’m not here at the moment …’

Oh God.

Stacey was sitting down but that didn’t stop her feeling her knees buckle. The moment she heard the voice of Jessica Matthews, her stomach seemed to rise up inside her, making her gag, and she could hear a rushing sound pounding away inside her head. She felt as though she were going to faint. A jigsaw puzzle of scraps of information instantly came together in her mind and formed a crystal-clear picture of the face of her friend.

Stacey held the phone at arm’s length and stared at it, mouth wide with astonishment, as though it were some alien piece of technology she had never seen before. Fragments from the profile of the killer flooded into her mind.

Intelligent. Methodical. Close links to the police. Possible medical background. Able to blend in perfectly.

It couldn’t be. Could it?

The bodies had been dumped in the area Jessica covered. She had been oh so pleased that Stacey had been assigned to the case and had helped her identify one of the victims – was it all part of a desire to play games? Scenes and snippets of conversations the two had shared in recent weeks replayed inside her head.

‘No one really gives a shit about people like that, do they? I know I don’t.’

‘I’ve always been fascinated by the workings of the human body.’

‘It’s nice to have someone on the team that I trust.’

‘Some men need to be taught a lesson.’

Could this really be happening? She had known Jessica for years; they had eaten dinner together less than a week earlier. They had shared jokes about men and work and other girly topics. They had worked together on dozens of cases. Could she have been hiding such a ghastly secret all this time?

Stacey thought back to the moment at the end of their last meal together when the waiter had dropped a tray. Everyone in the restaurant had jumped at the shock. Everyone except Jessica.

Now she heard Jacques’s voice in her head once more: ‘Research has shown that psychopaths and serial killers have a greater fear threshold, and are less likely to respond to fear-inducing stimuli or sudden shocks. Some researchers think they are virtually immune to those kinds of emotions.’

And that moment there was a heavy click on the line and a real voice sounded in her ear. Jessica Matthews had switched off the answering machine and answered the call.

‘Hello, is anyone there?’

Stacey said nothing. The seconds ticked by slowly before Jessica Matthews spoke again, first with a small giggle and then with a few softly spoken words. ‘I know you’re there. I can hear you breathing.’

Stacey was taken aback by the friendly tone. This just couldn’t be right. She had to be crazy. It couldn’t possibly be right.

‘Hi, Jessica. It’s Stacey.’

‘Stacey. How lovely. I was just thinking about you. What can I do for you at this late hour?’

Stacey did her best to think on her feet but too many things were happening at once, events were moving too fast for her to keep on top of them all. She was listening hard, trying to detect signs of – what? What exactly did psychotic serial killers sound like?

‘Oh, I was wondering if we could meet up in the morning. Maybe I could pop round. We could do that coffee we were going to do the other day.’

‘Sure, why don’t you come along to the hospital? I’ve got a meeting just before lunch but you can join me for elevenses. Hey, there’s a great new café near here called the Stone Bridge. The guy behind the counter is gorgeous.’

‘Really?’

‘Oh, yes. The moment I saw him I thought to myself, wow, who do I have to kill to get to go out with him? You know what I mean.’

‘Uh huh. Right.’

There was a pause before Jessica spoke again. ‘You and me, we’re the same, aren’t we, Stacey?’

‘Are we?’

‘Yeah. That’s why we get on so well. That’s why I’ve always tried to help you out. You remind me of me.’

‘Jessica … I … ’

‘I have to go now, Stacey. Way past my bedtime. I’ll see you soon.’

The line went dead. Stacey shuddered, then dialled a new number, an extension at the office where she knew the night team would be staffing the incident room.

‘DC Cooper speaking.’

‘Natalie. It’s Stacey. Do you have the toxicology reports from the case?’

‘I don’t think so.’

‘Why the hell not?’

‘They never arrived. We never got them.’

‘But you’re supposed to chase them up. That kind of thing should get flagged up. That’s what HOLMES is all about.’

‘They did get flagged up, and I made a manual adjustment to the file. I knew they weren’t going to contain any pertinent information so I cancelled the alert. I was just trying to save time.’

‘Who the hell told you? Who said they weren’t worth looking at?’

‘I … I … ’

‘Was it Jessica Matthews?’

‘No.’

‘Are you sure?’

‘It wasn’t.’

‘Then who?’

‘It was you. You told me. Last week.’

Stacey again thought back to her dinner with Jessica Matthews, the one when she had casually mentioned that the reports were not worth looking at, a fact Stacey had happily and trustingly passed on.’

‘Get hold of them now. And not from the pathologist’s office. Don’t even call them. Go direct to the lab. I want the originals. Nothing else. And I want them as soon as possible. I’ll call you later and let you know where to send them.’

There was one more call to make. Edward Larcombe was a veteran forensic pathologist whom Stacey had known for almost as long as she had been in the force. He could have retired years ago, but his skills and experience were in such demand that he felt almost obliged to continue working.

He answered the phone with all the world-weariness of a man who had become accustomed to having his sleep interrupted.

‘Hello?’

‘Edward. It’s Stacey Collins. Sorry to wake you up.’

‘Not a problem, my dear. If I wanted to only work nine to five, I should have become a filing clerk. What can I do for you?’

‘I need your help on a case. But this has to be off the record, strictly between the two of us.’

‘That sounds highly irregular.’

‘I know I’m asking a lot. I can’t explain right now, but you’re the only person I can trust. You’re the only person I can turn to.’

Stacey waited while Larcombe coughed noisily away from the phone. ‘What do you need?’

‘I need you to meet me at the mortuary at Guy’s as soon as you can. But you can’t tell anyone where you’re going or why you’re going there. Can you do that?’

‘Well, frankly I think I’m getting a little too old for all this cloak-and-dagger stuff, but, as it’s you, I should be able to be there in thirty minutes.’

By the time Edward Larcombe arrived at the hospital, Collins had made all the preparations. She led him through the entrance and past several bemused security guards to the mortuary, which was entirely deserted.