‘Same as before,’ Kate said, as she clambered out of the car. ‘Find a parking spot and meet me back here.’

As Finn pulled away, a gust of bitter wind rustled the damp leaves around Kate’s feet, and it was all she could do not to lose her balance as a shiver ran the length of her body. In daylight, Hilly Fields Park in Lewisham wasn’t nearly as menacing as it was in the darkness. She could imagine it in summer packed with children running around and city folk lying on the grass, topping up their tans. But in the middle of January, the grass looked old and withered and bore the marks of a torrid downpour, pockmarked with puddles.

Bisecting the expanse of green was a winding concrete path that led from the normally busy road, through the park to the all-girls school. She could hear muffled shrieks in the distance as one of the school’s sports teams participated in some event nearby.

Not prepared to risk slipping on the boggy grass, Kate stuck to the pavement and turned onto the path. The cold air on her face relieved the heat she could feel at the top of her scalp. She hadn’t seen Roxie O’Brien’s body in situ on the ground, as she hadn’t taken over the investigation until a month after she’d been found, but she’d seen pictures; naked with her skull smashed open with a hammer of some kind. She could almost picture O’Brien walking through the park when she was set upon by a man lurking in the dark. She’d read the report the scene of crime officers had produced, and they concluded there was no sign of a struggle on the grass beneath the body. They concluded that the murder probably occurred elsewhere and that the body was then placed on the grass beneath the tree.

Kate continued along the pathway, looking all around her, trying to determine why he had chosen this exact spot. In her mind, there had to be some relevance to the location, though that wasn’t a theory widely shared by her investigative team at the time. In fairness, there was nothing obvious about this or any of the other locations, other than that they were open spaces where the public would be likely to discover the body. But therein lay one of the problems with the theory: he’d taken a huge risk to leave the victims in such open places. Any number of witnesses could have happened upon him mid-act, but he’d managed to kill four times without being seen.

Finn jogged up behind her. ‘Is that where…?’

Kate pointed towards the tree. ‘Roxie O’Brien’s body was discovered just over there. Are you okay with all this? I know it’s a lot to take in.’

His face adopted a look of determination. ‘Absolutely.’

‘The forensic specialists examined every inch of the park, looking for any clue he might have left; but they found nothing. They did find a set of prints nearby, but couldn’t say for certain if they belonged to the killer. What shoe size are you?’

‘A twelve.’

‘The prints found were a size ten. That’s one of the most common sizes for male adults in the UK, so it didn’t narrow our search significantly.’

‘Were footprints discovered at any of the other crime scenes?’

‘Unfortunately not. Our SOCOs estimated the killer to weigh approximately 80 kg, which again failed to narrow the search. But it did make them more certain it was a man.’

Some members of her investigative team had taken to naming their mystery killer ‘Mr Average’. It wasn’t a view Kate subscribed to; having seen up close what he’d done to Steph’s body, she knew he was anything but average.

She observed the landscape around her, gazing at the tree as her head turned in full panoramic view. ‘Why here?’

Across the road from where Finn had dropped her were several three-storey townhouses overlooking the park. Anyone looking out of a top-floor window at the right time would have seen him carrying her into the park.

‘Do you think he wanted to get caught?’ Finn asked, unsure if Kate’s question had been rhetorical.

She shook the theory from her mind. ‘No, that’s not it. If he’d wanted to get caught he wouldn’t have stopped killing after Amy.’

In the distance, heavy cloud obstructed their view of the Canary Wharf skyline. The city she’d called home for so long seemed so far removed from where they stood, even though it was only a few miles away. If her ankle was healed, she could easily have walked the distance.

Coming to Lewisham today had been a bad idea. She’d hoped that seeing the scene in person once more would help shed some light, but it had only brought up more questions.

Kate took one final look at the tree, before turning and making her way slowly back along the path towards the main road. Finn went to collect the car. As she reached the pavement, she felt the first spots of icy rain on her cheeks. She tried to pick up the pace, but her crutch wouldn’t allow her to move any quicker. It was a relief when Finn pulled up a few minutes later.

‘Where to now?’ he asked, when she was back inside.

‘Finsbury Park tube station.’

‘Do you mind me asking: what are you hoping to achieve by revisiting these scenes?’

She stared out of the window as the drops of rain grew heavier against the glass, but before she could answer, her phone rang.

‘Ma’am, I’m sorry to disturb you on a Saturday.’

‘That’s fine, Laura. Go ahead.’

‘I thought you’d want to know, we’ve reviewed all the security-camera feeds from around the train station where Helen’s body was found, and we were unable to identify the exact time the BMW passed by. In total four vehicles fitting the description passed the area between eight o’clock on Tuesday night and the early hours of Thursday morning when the victim was discovered. None of the vehicles had the same registration number as Isbitt’s car.’

Kate clamped her eyes shut, pinching the bridge of her nose. ‘What are you telling me?’

‘I think the killer changed the plates on the vehicle to cover his movements.’

‘Why?’

Laura paused. ‘I spoke to SSD and they’ve confirmed an adhesive material was discovered in two places in the centre of both the front and rear plates. That’s why we weren’t able to find when the vehicle arrived at the scene.’

‘I’m going to compare the registrations of the four vehicles found on the footage against the PNC database to see if one stands out.’

‘That’s great, Laura, but listen, now’s not a good time. Why don’t you stop by my place tonight and we can go over it in more detail.’

‘Sure.’

‘Oh, and Laura, you’d better update Underhill with your findings, but when you do, please don’t mention my name. You know what he’s like.’

‘Understood, ma’am, I’ll leave your name out of it. Shall I bring food?’

‘You choose,’ Kate said as a fresh wave of nausea struck her. She hung up the phone.