‘We have to tell her.’ Kelly looked in horror at the screen, on which was listed in precise detail what could only be Zoe Walker’s commute to work.

‘Is it definitely her?’ Lucinda asked. Kelly and Nick were leaning over the DI’s desk, his laptop open in front of them. The lights were off elsewhere in the large, open-plan space, and the yellow strip light above Nick’s desk was flickering slightly, as though the bulb were about to go. Lucinda was working at a neighbouring desk, painstakingly checking each image on the website against the London Gazette adverts.

‘The description matches, the date of the listing fits, and Hallow & Reed is where she works,’ Kelly said. ‘There’s no doubt it’s her. Should we tell her over the phone, or go and see her?’

‘Wait.’ Nick hadn’t said much when Kelly had explained how she’d worked out the password. He’d taken one look at her phone; the small screen showing now a change to the text above the white box.

Log in or create an account.

He had dispatched the rest of the team home, with strict instructions to return at 8 a.m. the following day for another briefing. ‘Tomorrow’s going to be a long day,’ he’d said grimly.

It had taken them just seconds to fire up Nick’s computer and access the website. Far longer to try and get through to Finance; a process that, out of hours, was so frustrating that Nick eventually slammed down the phone and took out his own credit card from his wallet.

‘We can’t let the media get hold of this,’ he said now, ‘it would cause a riot. That means keeping it from Zoe Walker for the time being.’

Kelly took a second to compose a more appropriate response than the one that threatened to burst from her lips. ‘Sir, she’s in danger. Surely we have a duty of care to warn her?’

‘At the moment the situation is contained. The person – or persons – responsible for this website doesn’t know the police are involved, which means we have a chance of identifying them. If we show this to Zoe Walker she’ll tell her family, her friends.’

‘So we ask her not to.’

‘It’s human nature, Kelly. She’ll want to make sure other women she knows are safe. Before we know it, the papers will pick up on it and there’ll be widespread panic. Our offender’ll go underground and we’ll never find him.’

Kelly didn’t trust herself to speak. Zoe Walker wasn’t cannon fodder.

‘We’ll see her tomorrow and suggest she changes her route to work,’ Nick said. ‘We can give her the standard advice for anyone concerned about their personal safety; mix it up a little, don’t be predictable. She doesn’t need to know any more than that.’ He closed the laptop, sending a clear message to Kelly that the conversation was over. ‘You two can head off now, if you like. I’ll see you bright and early tomorrow morning.’ Just as he finished talking, the bell for the outside door sounded. Kelly went to answer it.

‘It’ll be the Cyber Crime guy,’ Nick said. ‘Buzz him up.’

Andrew Robinson had black-rimmed glasses and a goatee beard trimmed to next to nothing. He wore a grey T-shirt and jeans beneath a khaki parka he took off and dropped on the floor next to his chair.

‘I appreciate you coming by,’ Nick said.

‘It’s no bother. We’re snowed under at the moment, so I wasn’t planning on going home any time soon. I’ve had a look at your website. Whoever owns the domain name has paid to opt out of the WHOIS directory – that’s like a telephone book for websites – so I’ve submitted a data protection waiver to obtain their name and address. In the meantime I’m working on identifying the site administrator via their IP address, although my guess is they’ll be using a proxy, so that’s not going to be straightforward.’

Despite understanding little of what Andrew was saying, Kelly would have liked to have stayed to listen, but Lucinda was already putting on her coat. Reluctantly, Kelly did the same. She wondered how late Nick would stay working on the case, and if he had anyone waiting for him at home.

They took the stairs down to the ground floor. Lucinda’s hair was as sleek and shiny as it had been first thing that morning, and Kelly felt suddenly conscious of the unkempt crop that stood on end every time she ran her fingers through her hair. Perhaps she should dig out some make-up. Lucinda didn’t seem to be wearing much, but a slick of lip gloss and defined brows gave her a groomed, professional look that Kelly definitely lacked.

‘Where are you heading?’ Lucinda asked, as they walked towards the Tube station. She was taller than Kelly by a good couple of inches, with long strides that made Kelly move rather more briskly than usual.

‘Elephant and Castle. I share a flat with two other BTP coppers and an A & E nurse. You?’

‘Kilburn.’

‘Very nice.’

‘My parents’ place. Mortifying, at twenty-eight, I know, but it’s the only way I’ll ever be able to save enough for a deposit on a flat. Nick takes the piss out of me something rotten.’ She slipped behind Kelly as a woman in lurid leggings ran towards them, a bobble hat pulled low over her ears, and raised her voice to continue their conversation. ‘How did you find your first day?’

‘My head’s spinning. I loved it, though. It’s been a while since I was on an incident room; I’d forgotten what a buzz it is.’

‘What’s the deal with that, then? You were on the Sexual Offences Unit, right?’

Even though she had been anticipating the question, it still made Kelly catch her breath. Was Lucinda genuinely interested, or did she already know full well what had happened? Was she fishing for gossip? Kelly glanced sideways but the other woman’s face gave nothing away.

‘I was suspended,’ she said, the truth catching her by surprise. I left, she usually said, in advance of some cock and bull story about wanting more front-line experience. Or I was ill, which wasn’t far from the truth. She kept her eyes on the pavement in front. ‘I assaulted someone.’

‘A colleague?’ Lucinda sounded curious, rather than judgemental. Kelly took a deep breath.

‘A prisoner.’

Call him by his name, her therapist had reminded her on more than one occasion. Important that you see him as a person, Kelly, as human as you or I. Kelly had complied, but the syllables had tainted her tongue every time.

‘He raped a school girl.’

‘Shit.’

‘That doesn’t excuse what I did,’ Kelly said quickly. She hadn’t needed therapy to understand that.

‘No,’ Lucinda said. She paused, choosing her words carefully. ‘But perhaps it explains it.’ They walked in silence for a while and Kelly wondered if Lucinda was thinking about what she’d just said; if she was judging her. She braced herself for further questions, but none came. ‘You did a great job on that password,’ Lucinda said, as they neared the station. ‘Nick was very impressed.’

‘Was he? He didn’t show it.’ Kelly had tried not to care about the DI’s understated response to her discovery. She hadn’t expected a round of applause, but something more than a muttered good job would have been nice.

‘You’ll get used to him. I like his approach, personally. He doesn’t dish out praise readily, so when he does, you know you’ve done well.’

Kelly suspected she might be waiting a long time.

At the entrance to the Tube station a bearded man was playing a guitar, a hat on the ground in front of him, empty but for a few coins. His dog slept on a carefully folded sleeping bag, in front of a bundle of belongings. Kelly thought of Zoe Walker and her Crystal Palace busker.

‘If you were Zoe Walker,’ she said to Lucinda, ‘wouldn’t you want to know?’

They walked past the busker and into the station, both reaching automatically for their Oyster cards.

‘Yes.’

‘So …’

‘There are lots of things I’d like to know,’ Lucinda said firmly. ‘State secrets, Bill Gates’ PIN, George Clooney’s mobile number … That doesn’t mean it would be right for me to know them.’

‘Even if it’s the difference between staying alive and being murdered? Or raped?’

Lexi’s attacker had been following her movements for weeks, the police had concluded. Since the beginning of term, possibly. He was almost certainly responsible for the flower left outside her bedroom, and the notes tucked into her pigeonhole. Friends had brushed it off; laughed about her secret admirer. When the police asked if she’d noticed anyone following her, she told them about those Thursday evenings, walking home from her 4 p.m. lecture. The same boy leaning against the library wall, listening to music; the feeling of being watched as she walked away; the crack of a twig behind her as she took a shortcut through the woods. She wasn’t the only one who had felt like that, the police admitted. They’d had several reports of suspicious circumstances. Nothing concrete, they’d said.

Lucinda stopped walking and looked at Kelly. ‘You heard what Nick said; restricting this information is our best chance of finding whoever set up the website. Once we’ve caught him, the rest will be easy.’

Kelly was disappointed. She had hoped Lucinda might have sided with her; that she would use the influence she clearly had with Nick to persuade him to change his mind. Lucinda saw the look on her face.

‘You might not agree with his decision, but he’s the boss. If you want to stay in his good books, you’ll play by his rules.’ They took the Northern line together and the conversation moved on to safer territory, but by the time they separated at Euston, Kelly had already made her decision.

Rules were made to be broken.