‘OK. Well, let’s forget that for the moment. What do you know about Snapchat?’

‘Snapchat? Interestingly, I was just talking about this with someone in child protection.’

‘Why’s that?’

‘Because it’s a new preferred method for paedophiles to exchange images. Harder to trace than email or MMS. Or, at least, a lot of them think it is.’

‘Go on.’

‘Well, what Snapchat don’t make clear is that the images are saved into a folder on the user’s phone, and they’re easy to find if you know where to look.’

‘What if you don’t have the phone?’ Patrick asked. ‘Are they stored on a server somewhere?’

Bell cleared his throat. ‘According to Snapchat, they keep a log of the last two hundred images sent, but don’t save the actual images. Unless the image wasn’t viewed by the recipient. In that case, it remains on the company’s servers for thirty days.’

Patrick thought about this. It was most likely that Rose – and Jess, if the murderer had used the same method – had viewed the messages, possibly screenshot them for posterity. And the killer had taken the phones with him.

‘Hang on,’ Carmella said. ‘Could I log in as another user on my phone, if I knew their password, and view the images they’d received?’

‘No.’ Bell smiled patronisingly. ‘Because they disappear within seconds of being viewed.’

‘Shit.’

‘But if and when we arrest someone,’ Patrick said, ‘we’ll be able to look on their phone and, if they sent snaps to the two victims, they’ll still be there. Stored in a hidden folder.’

Bell nodded. ‘That’s right. Unless your murderer is tech savvy.’

‘We’d better hope he isn’t,’ Carmella said.

Patrick thanked Bell and watched him leave the room. He felt frustrated, like he was looking for a trail of breadcrumbs that had already been eaten by birds.

‘We’ll catch him,’ Carmella said. ‘He’s going to slip up at some point.’

Patrick stared into space. ‘Maybe. But how quickly? And who’s next on his list?’

Chapter 31

Day 10 – Kai

Kai slouched over to a corner table next to a massive poster reading ‘Home of the Whopper’, his laptop in one hand, and a plastic tray containing a box of cheeseburger and fries in the other. He dumped the items on the table and pulled back a red slatted chair, which made a loud metallic sound as it scraped across the tiled floor.

Opening the laptop with his right hand, he shovelled fries into his mouth with his left while looking around him to make sure nobody could see the screen. With greasy fingers he tapped in the Burger King Wi-Fi password and brought up the window of the OnTarget forum. He just needed to be sure about one or two things.

The thing that Kai feared more than anything was making Jade angry. She was angry a lot – he could just about deal with that – but the terror of one day making her so mad that she dumped him gave him a sick feeling in the pit of his belly that even half a burger in one big swallow couldn’t obliterate. His mates thought he was a total wuss – ‘pussy-whipped’, according to Ed – but he didn’t care. He loved her. And if this worked out like it should, Jade would be well pleased with him. He grinned to himself through the other half of the burger. He wasn’t going to let anybody upset his boo, no way.

He finished his meal and wiped his sleeve across his mouth before pushing the empty food box to one side. Hunched over the laptop, he laboriously typed a question with two fingers, then sat back and waited.

An answer flashed back in a minute. Kai tensed, read it silently to himself, lips moving, then relaxed and started typing again. It took less than five minutes to make the arrangements. Kai was dying to message Jade to tell her, but then decided not to, not until it was done. Then he reckoned she’d Snapchat him one of her special selfies – the kind that made him go soft and hard at the same time.

Leaving all his litter on the table, he pulled on his jacket and headed out on his mission. Pausing in the doorway under a blast of hot, stale air, he zipped up his laptop inside his jacket and smiled, a slow, smug smile.

Jade was gonna be proper pleased with him.

Chapter 32

Day 10 – Wendy

Wendy stood at the top of the escalators in the Rotunda, music from the PA system outside Frankie and Benny’s wafting over. Frank Sinatra. Her dad’s favourite. He liked that restaurant too, even if it was overpriced in his opinion. As a family they had eaten in places like this many times, before her dad had run off with the woman who was now her stepmother.

Every town had a leisure complex like this, usually on the outskirts, with a big cinema, numerous chain restaurants and a ten-pin bowling centre. Wendy was pretty damn good at bowling, even if she did say so herself, and had smiled when her new contact had sent her the picture of the bowling place at the Rotunda in Kingston.

‘Meet u here at 9.30pm’, the caption of the photograph had read before it vanished. She’d arrived ten minutes early to familiarise herself with the layout of the place. As she headed back down the escalator leading towards the basement bowling alley, she remembered the last time she’d played with her dad and sister. Her dad had taken her aside and told her how proud he was of her.

‘What, because I can beat you at bowling?’ she’d joked.

‘No, you numpty. Because of what you’ve done with your life. I’m dead proud.’

She smiled at the memory and for the umpteenth time in recent weeks felt a pang. She missed her broken-up family. Once this case was over she was planning on taking some leave, going back to Wolves to see them.

But before that, she had a chance to make her dad even prouder. The chance to make a difference to this operation.

Now that she was familiar to most of the users of the forum, Wendy had decided it was safe to mention the murders without arousing suspicion that she was a mole. There were already lots of threads about it, discussions of the vigil that had taken place, and immediately after the deaths of both MissTargetHeart and YOLOSWAG, the site had been filled with intense, borderline-hysterical tributes to the dead girls.

MissTargetHeart helped me when I was stressing about my exams . . . She’ll be singing with the Angels in Heaven now.

Me and YOLOSWAG hung out after the Wembley concert last summer. She had Shawn tattooed on her skin and on her soul. R IP SISTER!!

So, earlier that evening at her desk, Wendy had started a thread: I haven’t told anyone about this, not even my mum, but ever since what happened to those poor girls I have been terrified. I keep hoping the fact they were both OnT fans is a coincidence but what if it isn’t? I have a theory about what happened to them but I’m too scared to share it on here.

This post had sparked a flurry of responses, most of the girls demanding to know about her theory.

I can’t say, Wendy wrote. I wish I’d known them like some of you did. Then I might be able to prove my theory is right.

The conversation went on from there, mostly going in circles. Wendy waited for Jade and some of the other regulars to join in, hitting refresh repeatedly, frustrated that no-one was taking the bait.

Then a message popped up in her private inbox, headed ‘YOUR THEORY’.

It was from a user called Mockingjay365, whose profile picture was of Katniss from The Hunger Games, bow and arrow pointed at the camera.

I’d luv to here about ur theory, the message read.