Anna toyed with not going to see Shaw at all. His promise of giving her some more ‘special information’ about Krastev and his link to Abbie’s death smacked of more Shaw-style manipulation. Dawes was right about that. She could have made her excuses, insisted that he send her what he knew by letter. But now that they’d found the tunnel under the fence, she’d decided, reluctantly, to quiz him again. See if he’d been hiding anything else from them.

Anna went alone. She didn’t have to, but it would be a lot less hassle and would spare the other members of the team the simmering indignation she’d seen in everyone who accompanied her. Holder and Dawes both seemed to simply provoke Shaw. Khosa, on the other hand, could not stand being near him. For her it was like a fear of snakes.

Shaw’s smug, goading persona did that to everyone. Of course, Anna remained naturally wary. But she realised, as Shaw was led into the poky, soulless interview room at Whitmarsh prison to meet her yet again, that she was not scared of him. He’d attacked people across the desk separating them, this very table, yet, as unpredictable as he was, she was certain he had no desire to harm her. What Anna saw was a man driven by deep anger and a need for vengeance.

‘Must be starting to feel like a home from home for you, this room, Anna?’ Shaw said in his slow, Mancunian drawl as he settled himself on the plastic chair.

Anna didn’t grace this with a reply. Shaw’s bravado felt slightly desperate for once and she quickly analysed that impression. He was paler, thinner even than when she’d last seen him. He’d lost fat from his face, and his eyes, behind the thick lenses of his glasses, looked puffy and red, though they’d lost none of their calculated cunning. Shaw held some folded sheets of paper in his hands. He placed them on the desk and covered them with his hands.

‘Is that it?’

Shaw nodded.

‘Why didn’t you give the original investigators this information?’

‘Because they didn’t want to know. Besides, they weren’t you, Anna.’ He gave her one of his slow blinks.

‘I’m looking forward to reading it.’

‘The governor gave me some shitty paper to write on but denied my request for access to a computer. For checking dates.’ Shaw’s smile told her that he had not expected anything less. ‘Didn’t matter.’ He tapped his temple. ‘It’s all up here anyway.’ He made no effort to hand the sheets over. ‘How about I give you the gist once you’ve told me what you and the team have found, eh?’

Shaw possessed no bargaining power here, not really. They both knew she could have the prison guards take the papers from him at any time. But they’d struck a deal and the sensible thing to do was not antagonise him. Anna had a feeling, too, that Shaw might retain certain vital bits of his story for just these sorts of situations. And then there was the tunnel.

‘OK,’ Anna said. ‘We’ve confirmed Krastev worked as part of the construction crew contracted to build the upgrade to the secure unit at Ryegrove Hospital in Bristol. It’s the fence you can see from the spot you took us to on the railway line. The second body was a nurse who worked at Ryegrove. So far we’ve found no link between her and Krastev.’

Shaw frowned. ‘Krastev got his kicks from watching kids kill themselves and helping them take the final reluctant step. “I am only facilitator.” That’s what he said to me. As if it justified the bastard’s actions. But someone told him what to do.’ Shaw’s lids dropped as if he was remembering something unpleasant. ‘Just like they told the Black Squid administrators what to do.’

‘The administrators?’

‘The bastards who manipulated the kids. The scum I killed. They weren’t all meant to die. I made mistakes, got too angry. But they weren’t the real monster behind the Black Squid, we both know that.’

Anna sat up. The reports she’d read of Shaw’s victims indicated he’d tracked them down. They were all different but shared one common feature of having dabbled in chat rooms, grooming victims for the Black Squid game. It was assumed they were part of a network. ‘Are you saying the administrators were being made to do what they did, too?’

Shaw nodded. ‘They were only halfway up the food chain. The Black Squid is the real apex predator here.’

‘I don’t follow.’

‘Krastev was a sick bastard. He did what he did because he liked to. But the others I got to were just sad shits the Black Squid got its tentacles around and squeezed. It’s how the Squid works. It finds you online, somewhere you really shouldn’t be, and sucks you in. Maybe it makes you admit your weaknesses, then it starts to manipulate you. Being online should carry a government health warning, you know that?’

Anna nodded, letting him have some space. Eventually he continued.

‘Once the Squid has one of these sad bastards on the hook, they become an administrator in the game. The Squid makes them do the dirty work. Sets them targets. A kill score. And it’s easy for these creeps because it isn’t real. It’s play-acting. Their stage is suicide chat sites. They pretend to be someone who’s been through it all, or a caring doctor, or another teenager in pain. Before you know it they’ve suckered in another vulnerable victim like Abbie. And once that victim trusts the administrator, they make them feel like there is no way out of the “game” but to end life itself. And all the while the real killer is once-removed, watching, manipulating with his fucking tentacles.’

‘Then we’re talking coercion, blackmailing people to be groomers. But why?’

Shaw gave her a slow blink. ‘I know people think I’m an evil bastard, but this bastard has no conscience. It’s killing by remote control. For the exhilaration. The sheer evil thrill of it.’

‘So even after what you did to the administrators, you were no closer to the Black Squid himself?’

‘Oh, I was. The administrators knew nothing, but Krastev did and he gave up the last site at Bristol very reluctantly. That’s why I know it’s important. He was desperate not to tell me about it. It’s where the answer lies, Anna.’

Shaw unfolded the papers under his fingers. ‘Three addresses for more buried treasure. One in Leicester, one in Devon and one in Cheshire, in the Wirral. Krastev liked to move about.’

Anna took the sheets and glanced at the handwritten locations. ‘Is that it?’

Shaw stared at her, amused by her reaction. ‘No need to be sniffy. I was going to make you go on three trips with me. Of course, if you prefer that?’ He grinned and then let it fade away. ‘Fact is, I might not be here to go with you.’

There it was again. The uncharacteristic gloom.

But he wasn’t finished. ‘When they looked at Abbie’s case, they were clueless. In those days, digital forensics were like cave paintings to most coppers. And chat rooms had better anonymity than Swiss bank accounts. It’s worse today with all the bloody social media companies bleating about freedom of speech and data protection.’

‘So I’ve been told,’ Anna said, remembering Varga’s concise assessment.

‘But when Abbie was killed the Black Squid had rules for the administrators. Verification is what it was all about. In the days before Snapchat and social footprints, that was Krastev’s “job”.’ Shaw made quotation marks in the air with his fingers. ‘These days there’d be no need for him. He’d be a waste of space. Today you can get proof of action in an instant. Like that poor kid who took a selfie of herself before she jumped off that cliff. The Squid wants that. He gets a kick from knowing the victim has a mother and a father and brother or a sister. If one of them saw that image they’d have to live with it the rest of their lives. I have to live with what Krastev told me about Abbie. It’s the last thing I think of when I go to sleep and the first thing when I wake up.’ Shaw’s focus drifted off towards some inner memory. When he looked up, his expression was solemn, his eyes black coals in his pale, anaemic face.

‘You’ve got a chance to stop this, Anna. You can get rid of this stinking piece of shit before someone else treads in it. He’s frightened of the one thing he has no control over. That one little mistake he’s made that he thinks no one is looking for. Something he and Krastev couldn’t hide behind their computer screens. They think they’re invisible. But they aren’t. I’d say you need to ask yourself three key questions. Why those railway tracks? Why has there been a gap in the Black Squid killings? And what was Krastev doing at Ryegrove?’

‘We’ve found a tunnel under the fence. My guess is that Krastev was responsible for that. That’s why I came here, Hector. To see if you knew—’

Shaw shook his head. ‘I’m not doing well, Anna. I can see it in your eyes, too. No one’s said it yet but perhaps it’s the big “C” eating away at my marrow. I’m relying on you to finish the job that I started. I fucked up. Make sure you don’t. And do I feel sorry for what I did? No. Rabid dogs need to be put down before they infect another. When you get to the Black Squid, remember that.’

Anna did remember that. Remembered it more than anything he’d said as she drove back to Bristol.

The rabies virus caused hydrophobia in its victims. Despite horrible thirst, any attempt at drinking, or even the suggestion of drinking, caused excruciating spasms in the throat and larynx. A slow strangulation. Enough to drive most infected mammals mad.

That word haunted Anna. Was it what Shaw was implying here? That the Black Squid was mad? Or simply bad?

She’d met several criminals whose humanity had long since packed a suitcase and gone on extended leave. These were the people who could no more empathise with their victims as recite the words to ‘Supercalifragilisticexpialidocious’ in Latin. She’d come face to face with the ‘bad’ on more than one occasion. People who genuinely wore a cloak of evil.

But then the general public, and often her colleagues in the force, needed to believe that criminals, especially those involved in heinous crimes, were in some way unhinged, in order to explain away how anyone could behave in that way. In Anna’s experience though, true madness was rare, and most serious and violent crimes had their roots in pettiness and heightened emotions and the red mist of sudden loss of temper.

But there were exceptions.

And she had no doubt in her mind that some criminals she’d dealt with were not normal. Were indeed perhaps a little mad.

The word brought her up short once again as her thoughts ricocheted in a new direction.

Was that what the thinking had been with Aunty Mary? Anna knew this little bit of mental gymnastics paid no heed to logic, but she could not help herself from wondering if these were the terms of reference those around her had applied to poor Mary. The same thinking that her mother had perhaps applied to her unconventional daughter. Was that what was behind the disinhibited words her mother threw out like emotional grenades these days? This insight, pushing through the thin wrapping of denial Anna’d used to paper over their relationship, suddenly stuck its reptilian snout into the air and flicked a forked tongue. It made Anna think. It made her pause to wonder if, had she been born a generation before, her childhood social awkwardness, her need to be alone in her own head, her lack of warmth towards others might have led to a label and a misconstrued diagnosis with ECT as the only ultimate treatment.

She knew how irrational all this was and yet her memories of the frightened, broken, mumbling woman Aunt Mary became, alone and abandoned in Talgarth asylum, played out like a Dickensian scene in her head. Mary’s drug-addled brain rendered her unable to articulate her fears and thoughts. Had Anna, even as a frightened child, seen herself reflected in those terrified eyes?

Her work phone’s tone dragged her back to the moment. Dawes’ voice was a most welcome intrusion.

‘Ma’am, we’re at the Norcott place in Wales. House is empty. My guess is he’s off his meds.’

‘Based on what?’

‘Based on the twenty unopened boxes of happy pills in the barn. He’s been here, all right, but preferred the barn to the house.’

Anna remembered Beth Farlow’s words. ‘His mother blamed him for the accident and refused to talk to him afterwards. She refused to have him in the house. Made him sleep in a barn.’

‘There’s a newspaper here from four months ago,’ Dawes said. ‘I reckon he’s been in the wind since then. And there’s some other stuff here, ma’am.’

‘Like what?’

‘I’m sending you a photo. We’ve only just got a signal and that’s after driving five miles back towards the main road. Should be coming through now.’

‘OK. It’s not through yet. I’ll ring you after I’ve seen it.’