‘I’m telling you, Lilian, it’s more than that. It feels … I hate to say it … supernatural.’

‘Hold on to your horses there, Donal,’ she smiled, ‘let’s keep this in perspective. What’s happened here is that a hallucination may or may not have helped you spot a contradiction in a statement. Looking at it in a cold scientific light, Karen had made that mistake irrespective of your visions. At our most optimistic, what you’re exhibiting here is an ability to use your disorder to make you better at your job. I think that’s potentially really interesting. We don’t need to … cheapen it with second-rate science fiction.’

I couldn’t let that go: ‘Yes, God forbid something comes up that doesn’t fit neatly into one of your approved little scientific boxes.’

She threw me that look of hers, the one that said, This guy is a weirdo.

‘What we need to show now is a consistent pattern of this happening to you. To use police parlance, we need to build a case.’

‘And that would be enough for your dissertation?’

She nodded and smiled: ‘I think the fact we’re even having this conversation is amazing, Donal.’

‘Great,’ I said, but I couldn’t help feeling that her cold scientific light was failing to illuminate the bigger picture.

By the time I rang Gabby it was after ten p.m. and she sounded knackered. I promised to call her much earlier tomorrow and take her out for dinner.

‘A proper date?’ she asked.

‘There’ll even be candles,’ I assured her.

Chapter 25

Clapham Police Station, South London

Tuesday, August 13, 1991; 10:00

Next morning, I clicked open the forensic report and began re-reading intently.

Now that Marion’s daytime appearances had proven relevant to the case, I felt convinced that her night-time attacks also held clues to her killer. To crack this case, all I needed to do was decipher her macabre nocturnal charades.

The theme of both her visits had been slamming doors. I concluded that she must have been leading me to the front door of her flat. The key to finding her killer must somehow be connected to that door. I just needed to figure out in what way.

We knew already that the fingerprints of Peter Ryan and Karen Foster had been found on both the front door of 21 Sangora Road and the door to Marion’s flat. This fact in isolation was evidentially useless. But what if Karen had carried out the crime with another, unidentified male accomplice? The violence of the attack meant it had to be carried out by a man. Was that what Marion had been trying to lead me to? Was there a third person we hadn’t identified?

Forensics had found sixteen unidentified prints on the front door, seven on the flat door. None of them matched known offenders. But did one of these prints belong to the muscle; the knifeman? This had to be what she’d been trying to tell me. I needed to identify the owners of those twenty-three unknown fingerprints. But how?

Marion was clearly security-conscious, cautious. I figured that she wouldn’t have let Karen into her flat with a stranger; Karen probably knew better than to even try. Whoever she recruited, Marion must have known at least by sight or by first name. The common denominator could only be the Pines care home. Peter and Karen worked there. Peter and Marion lived there in staff accommodation for seven months after their marriage. I decided to ask Shep if we could take the fingerprints of every employee at the home, including contractors and any workers who’d left within the past year. If we cross-referenced their prints with those found at the scene, I felt sure we’d find the missing link in this case. Well, it was the best I could come up with.

Shep said he’d only sanction this expensive and time-consuming operation if they got nothing out of today’s interview with Karen. He seemed more ratty and irritable than usual.

‘You okay, Guv?’

‘No I’m not fucking okay,’ he spat.

He looked at my startled face and softened: ‘I’m just back from Marion’s family. I had to tell her mum and dad that Peter used to go out with Karen Foster, and that they may have resumed their affair. I might have known he wouldn’t have had the balls to tell them himself. They took it badly. I had to call an ambulance for Mary.’

‘Christ,’ was all I could think to say, then: ‘Surely he can’t carry on staying with them now?’

‘My worry is, if Peter moves out, his family or friends might convince him to do a midnight flit to Ireland. You know what the extradition situation is like right now. It could drag out for years. And we haven’t got enough to charge him.

‘So I had to ask her dad John – would you mind keeping him a bit longer. While I’m asking him I’m thinking, “if he’d done that to either of my daughters, I’d have thrown him out the fucking top floor window.” But John agreed, right away. “If it helps catch Marion’s killer, we’ll do it,” he said. Can you imagine? They’re living fucking saints, that family.’

Shep’s voice cracked and eyes moistened: something I hadn’t seen before.

‘Anyway,’ he coughed, instantly regaining control, ‘Mick and Colin are limbering up for Karen’s interview. Why don’t you come and watch with me? I could use a spare set of eyes and ears.’

I remembered those dank, fusty interview suites from when I’d made my statement the day after Marion’s murder. As we walked along that single long corridor to the adjoining block, Shep explained that Karen Foster had been formally cautioned and brought in first thing. Peter Ryan had agreed to come in voluntarily at ten a.m. tomorrow.

When we came to the security doors, Shep dialled in the code and invited me to go through first. I pulled down the handle and pushed.

‘Put your shoulder into it, man,’ he said. It was another one of those tightly-sprung, self-closing fire doors. My mind shot back to Marion’s flat: what the hell was I missing on that door?

I pushed it open, held it for Shep, then followed him along more corridors and left into a small kitchenette. Like two prize fighters pre-bout, Mick and Colin stalked about, psyching themselves up, mentally ordering their verbal combinations.

Shep brought them up to speed on the loose ends from last weekend’s purge of Peter’s workplace, the Pines care home. ‘As we know, Karen took a few hours off work. She told colleagues she was going shopping in Blackheath with her younger sister, Laura. One of the nurses there, Sharon Healy, finished work at four p.m. and saw Karen driving her purple estate car out of the clinic car park. She was alone, with her hair tied up, wearing shades and a red top. Colleagues report her wearing a red top and jeans throughout that day and evening.

‘Another employee, Valerie Donald, left the clinic at six p.m. on the dot. She knows this because she has to pick up her kid from childcare. She saw Karen’s purple estate car stationary at the end of the driveway, facing towards the home. Sitting inside it was Karen still wearing her shades and, she thought, a dark top. She remembers Karen waving back at her.

‘The question is, of course, what had Karen been up to in those intervening two hours? And with whom? What’s your strategy, gents?’

‘We don’t want her clamming up, so we’re going to take it nice and gently,’ said Colin.

‘We’ve got all we need to peel her open like a can of sardines,’ added Mick, calm but focused, ‘there’ll be no need for bawling and shouting.’

‘Follow me, Lynch,’ said Shep, careering up the corridor and through a door.

‘Ringside,’ he said, taking the furthest of four seats facing a window. On the other side of the glass, Karen sat nearside of her duty solicitor, her arms folded, chewing a piece of gum. She might have been waiting for a bus.

‘She can’t see us, right?’ I whispered.

‘Or hear us,’ boomed Shep.