I haven’t seen you on the forum before, Wendy replied.

Don’t post much, usualy just read. Im not very good at riting. Too shy.

I understand, Wendy wrote, unsure if this girl was a time-waster. I wish I’d known Rose and Jess.

I new them.

Really?

Yeah. We used to hang out, talk about OnT. Met them outside BBC last yeer wen OnT were on Graham Norton.

Wendy waited.

I think I no sumething. About an enemy they had. They were talking about it.

Wendy’s pulse increased. Though the chances were Mockingjay365 was talking nonsense. She typed: An enemy? Have you been to the police?

No! My dad hates feds. He sez they are bent. He wd kill me if I talked to cops.

I understand. Who was this enemy?

The answer came back straight away. I’m scared. He knows who I am. And he knows that I know him.

You can tell me. He won’t be able to read this.

There was a long, frustrating pause. Eventually, a response came. I dunno. My dad sez that any1 can spy on u on the internet. Like wen Jennifer Lawrence’s nude pics got hacked.

Wendy supposed it made sense that a Hunger Games fan would be extra paranoid about Internet security after the naked selfies of that film’s star had been stolen and posted online.

We cd meet? Mockingjay365 wrote. I saw you said you was local to me – Kingston?

It was Wendy’s turn to hesitate. Was it worth it? Could this girl really know something? This talk of Jess and Rose having a common enemy was intriguing, but could be a fantasy.

Yeh. Where? she typed, playing for time and looking up from her computer. It had just gone eight. She decided she would find Patrick, ask him what she should do. That was the correct protocol. So she hurried towards his desk, disappointed to find that he wasn’t there.

‘Looking for Lennon?’

She turned. It was Winkler, gym bag in hand, his eyes blatantly roaming up and down her body as he waited for her response.

‘Yes, I—’

‘He’s having a party, so Masiello let slip earlier. A surprise birthday dinner with Masiello and his mad missus and the guv.’ He sniggered. ‘That should be awkward. Pretty disgraceful, though, if you ask me – having a lovely dinner party when proper cops like you and me are hard at it trying to stop a murderer.’

She didn’t point out that he looked like he was heading to the gym.

‘Anything I can help with?’ he asked, taking a step closer so she could smell his aftershave.

‘No . . . It’s fine. Thanks.’

She hurried back to her computer and saw that Mockingjay365 had suggested meeting at the Rotunda. She tapped out a reply: OK. What time? And where exactly?

Do u hav Snapchat? came the response.

She didn’t, but she could download it.

Username same as on here. Add me & Ill message you. Snapchat deleets so no1 can trak it.

And now here she was, standing outside the bowling alley waiting for another message, hopefully with a selfie of her new contact so she would be able to recognise her. At least it was warm in there – it was freezing outside, cold enough to snow, and if Mockingjay365 didn’t message her in the next five minutes, she was going home, back to her flat for a hot bubble bath, a glass of wine and the next episode of The Good Wife. And maybe to indulge her fantasies about a certain detective inspector. She hoped he was enjoying his birthday – Valentine’s Day was such an apt day for someone so sexy to be born – but couldn’t help but wish she was at the dinner party. She imagined herself as Gill there with him, laughing, Patrick squeezing her knee beneath the table, forgetting about the case for a couple of hours and enjoying himself, relaxing, and after their guests were gone he would take her/Gill to bed and gently lay her down and . . .

Her phone beeped, shaking her from her fantasy. Hot shame flooded through her. What was she like, thinking about such a thing? Patrick, DI Lennon, was married and she was on the way to meet someone who might help her find the murderer. She needed to stop thinking about him. The sensible thing would be to ask to transfer to another team, maybe even another station. When this case was over, maybe that’s what she should do, after she’d visited her folks. She would work it out later, but she was glad now she hadn’t left that card on his desk as she’d intended.

She took out her phone and saw, with a mixture of relief and anxiety, that she had a new Snapchat message. It was a photo of the café inside the bowling place, with another caption. ‘I’m here, waiting.’

Wendy had changed into her teenage disguise at the station: skinny jeans and a parka with a furry hood, trainers and the make-up that, she hoped, made her look ten years younger. She pushed through the double doors of the bowlplex and headed towards the café.

The noise in here was incredible. From the back came the clatter of bowling balls, the crash of scattering pins, whoops of delight and groans of disappointment. Above that came the cacophony of noise from the arcade machines that took up a large area – driving games and air hockey, machines that spat out chains of tickets that could be exchanged for cheap prizes. A woman stood feeding coins into one of those machines with a large claw, trying to win an Angry Birds toy. The place was full of teenagers and kids who, Wendy thought, should be at home in bed at this hour. There were even some toddlers running about.

But there was no sign of anyone who might be Mockingjay365. She scanned the tables in the café. Lots more teens and families scoffing burgers and soggy-looking pizzas. The smell of nachos reached her nostrils and her stomach growled, reminding her that she hadn’t eaten anything since she’d had a dry egg and cress sandwich at lunchtime.

Where the hell was Mockingjay?

Right on cue, her phone beeped. She had a new Snapchat message. It was a photo of a car park. The caption read: Im in the car park round back. My ex is in Rotunda. Dont want him to see me!!

Wendy tutted. This was getting ridiculous now. But she walked back up the stairs to the ground floor and pushed through the double doors into the freezing air.

She strode along the pavement by the one-way system, eyeing the cars and buses moving in the same direction, wishing she was cocooned inside a warm vehicle, not out here in the bitter wind. There were plenty of people around, mostly teenagers heading in and out of the Rotunda, but as Wendy turned right towards the back of the bowlplex, the noise from the cars and people dropped away to be replaced by near-silence.

Wendy checked her phone again, then looked around her. She was standing in a residential road around the back of the Rotunda. Across the road was a car park on the ground floor of what looked like private flats. That must be where Mockingjay was waiting for her.

Wendy hesitated. It not only went against her police training but her instincts as a woman: you didn’t go into dark, deserted places like this on your own. She badly wanted to talk to Mockingjay – the girl was her only potential lead – but how did she know she could trust her? She could be anyone.

She sent Mockingjay another message. I’m outside the car park. Come out. There’s no-one else here. No need to be scared.

There was no response. Still holding her phone, Wendy made a decision. She would call DI Lennon, let him know what she was doing. He’d given her his mobile number in case she had anything important to tell him. Well, this qualified.

His phone rang five or six times before he answered.

‘Boss? It’s Wendy . . . Listen, I . . .’

‘Oh, Wendy. Is it life or death?’

Wendy hesitated. She heard a woman’s voice calling Patrick impatiently.