We followed him into a typical box room with crayoned drawings on the wall. A little girl lay sleeping, face up, on the bed.

‘He came in here, sexually assaulted the child, Jazmine, aged four, and smothered her. We can’t be sure in which order yet.’

A spasm reversed my swallowing mechanism. I stopped the gag reflex just in time.

‘But that’s not the worst of it,’ said Kenneth in his jovial, sing-song Welsh accent, leading us into the sitting room.

‘What in the name of God?’ said Shep.

I peered round his shoulder.

My mind felt like a misfiring one-armed bandit, reels spinning in different directions. I simply couldn’t absorb what I was seeing.

I heard Ken say: ‘He sliced her torso open from the pubic bone up to her throat and pulled her ribcage back to expose her organs.’

‘Like some sick work of art,’ said Shep.

‘He’s taken part of her stomach, we presume as a trophy. The sick fuck covered her in tea towels so that whoever came on the scene first – which turned out to be Samantha’s partner – had to unwrap his masterpiece.’

Just like that, every bone in my body turned to liquid. Fully conscious, my knees buckled and I keeled slowly, head-first, into the carpet, sliding down in front of Samantha’s lovingly butchered corpse.

‘Oh for fuck’s sake,’ said Shep as I lay there, helpless but still lucid, a beached whale.

‘Get him outside,’ ordered Ken.

Two uniformed officers yanked me to my feet and carried me out of the house. As they hauled me through the hallway, I could feel my helpless feet skidding along the ground, bouncing off the thresholds.

‘Fuckin’ poof,’ muttered one of my bearers.

‘Should think about another line of work,’ said the other.

I could see the crowd pointing, laughing.

‘Fucking hyenas,’ said the first officer.

‘What would you expect in East London?’ said the second.

The two paramedics took over. One of them looked into my eyes. ‘You can hear me, can’t you?’ he said. All I could do was nod and blink twice. ‘He’s fully conscious,’ he told his partner, ‘this is weird.’

They bundled me skilfully under the police tape and hauled me to a patch of grass on the other side of the road where they laid me out in the recovery position. Within seconds, I felt myself recharge from the feet up. Finally, I hoisted myself into a sitting position and helped myself to a few greedy lungfuls of air.

I was a frequent fainter as a kid, nutting more carpet than a devout Muslim. I knew what it felt like to pass out. This had been different. I had remained fully cogent throughout. I hadn’t even felt queasy. My body simply gave way. I could see and hear everything.

‘Are you narcoleptic, mate?’ asked the kinder-faced paramedic.

‘Not that I’m aware of. I am being treated for insomnia.’

‘You need to tell them about this. It could be cataplexy.’

‘What’s cataplexy?’

‘It’s when an extreme emotional experience causes your muscles to seize up. It can be triggered by anything really, shock, love, even finding something funny. I’ve only ever seen it in narcoleptics though.’

‘Should I be worried?’

‘There’s no long-term damage and it usually only lasts a few minutes. But lying about helplessly on the streets of London is never a good idea. Definitely mention it to your specialist.’

Despite what everyone had assumed, it wasn’t the gore that had knocked me over. It was the shock of confronting the unthinkable: had I let Marion’s killer remain free to do what I’d just seen, to slaughter a mother and her four-year-old daughter? If Samantha and Jazmine died horribly because of my mistake, how was I supposed to live with myself? How could I ever atone for that?

The sound of a car braking hard snapped me back to the here and now. Out jumped Fintan, his fat panting snapper in tow. I crawled behind the tree trunk but the fucker had better radar than a bat.

‘So they are linking it?’ Fintan gasped shamelessly. ‘Christ, I told you, didn’t I? Forty-nine stab wounds in a domestic? It’s unheard of. So, he’s done a mother and child this time?’

A pair of violated corpses suddenly felt like better company. I scrambled to my feet and headed back to the crime scene, meeting Shep on his way out.

‘Didn’t know you were the squeamish sort, Lynch,’ he said.

‘Neither did I, Guv. Fintan’s turned up.’

‘Let’s get the fuck out of here,’ said Shep, setting off at his usual lightning pace.

It was too late: Fintan’s baboon hosed us down all the way back to the car. ‘How many photos of us do you need?’ Shep shouted.

We hopped in like fleeing bank robbers. Shep gunned the engine, tried to run down the snapper then took me through what I’d missed.

‘I hate to tell you, but that murder has a lot in common with Marion’s.’

My stomach swapped places with my mouth.

‘There’s no sign of a forced entry. She was attacked with a knife near her front door. It was frenzied.’

I closed my eyes as hard as I could and rubbed my face.

‘So what are you going to tell the Commissioner?’ I finally managed to ask.

‘I have to tell him that they could be linked, because they could be.’

The world fell silent.

‘Of course, Ken was right. We won’t know for certain until the reports are in. But the media will link the attacks right away. They won’t be able to resist it, climbing onto their high horses and demanding to know why we haven’t caught this maniac targeting vulnerable young women in their homes. For them, it’s a Godsend.’

‘What if I’ve fucked up?’

Shep sighed hard: ‘There’s only one way to fix this, Lynch. We’ve got to gather enough evidence to charge Karen Foster. And we’ve got to do it quickly. As soon as she’s charged, you’re out of the woods.’

I wondered when and how I’d found myself in ‘the woods’, but patently I was in them alone. But at that moment, Shep was the only person who could save me. He must have smelled my desperation. ‘Fuck it,’ he said, performing a joyrider’s emergency stop. ‘Run over to that phone box. Ring the incident room. Tell whoever answers that the team needs to call their families. They won’t be home tonight.’

Chapter 29

Clapham Police Station, South London

Wednesday, August 14, 1991; 17:30

Shep called a wildcat briefing. He told the assembled team that, as yet, there were no definite links between the murder of Marion Ryan and the Bissets in East London – and that we should ignore any media reports saying otherwise. McStay sniffed and gave Barratt the eye. He wanted so badly for us to be wrong. I decided to watch his smug face as Shep delivered the rest of today’s news, starting with the interview suite revelations.

‘Peter Ryan admitted today that he slept with Karen Foster two weeks before Marion’s murder.’

He gave that statement plenty of air for dramatic effect.

‘That same night, Peter told Karen that he was giving up their twice-monthly Monday night trysts, thereby ending their affair. He also told her that he and Marion were moving to Ireland. Because Marion was pregnant.’

Even my neck hairs stood to attention: and I already knew about it.

‘By telling Karen this news, Peter effectively signed his wife’s death warrant.’

McStay’s nose turned the colour of a scalded bellend.

‘Marion wasn’t pregnant, but Karen Foster didn’t know that. She and an accomplice murdered Marion and, as far as she was concerned, their unborn baby because she wanted Peter Ryan all for herself. The challenge now lies in proving it. We have no weapon, no witnesses, we still haven’t found a hole in her alibi and, as for forensics, we need a fucking miracle.’

He took a deep breath.

‘I’m asking each of you to give it one last push. Not for me, but for Marion and her family.

‘The murder weapon: I want a team to carry out a search of Karen’s parents’ home in Lee. Maybe Karen and her accomplice went there to pick up the murder weapon before driving to Marion’s flat.