On Thursday morning, the team sat in the incident room, the mood one of general dejection. It had been a week since the fire at the hospital. Too much time had passed and too little evidence had been uncovered. The killer they were hunting had been allowed to get away with too much in the time that the team had spent chasing their own tails, leaving them unable to join the dots between the various points and people of interest that had arisen.

Alex’s tiredness was ingrained in the furrows of her brow, and despite the two coffees she had already consumed since arriving at the station, she feared it was set to remain with her for the duration of the day. She had barely slept. She hadn’t been able to tear herself away from thoughts of Gary Peters and Doris Adams. The gruesome details of their post-mortem reports had lingered through the night, haunting her with their horrific truths. Corey Davies, terrified of his own shadow. And then there was Christian Coleman. Alex had no evidence to suggest that he had been responsible for the abusive graffiti that had been scrawled across the front of her home, or the cut brake line that had caused her car accident; just an aching, relentless suspicion that couldn’t be shaken off.

She knew she should have been to see him by now, but a deep unease was keeping her from going to the house. It wasn’t just Christian, she realised that. What had happened to Chloe earlier that year still haunted Alex as much as it did Chloe. They exposed themselves to new dangers with every case. It was only a matter of time before something caught up with her, and perhaps that time was now.

Alex had arrived early at the station that morning, but Youssef Hassan had got there before her. His admission was unexpected; it came as little surprise that he was responsible, but she hadn’t anticipated the guilty party coming forward to confess his crime. The family’s financial problems – ones that he had managed to keep hidden from his wife for months – had driven him to the arson attack, but with his eldest son under suspicion he had been forced to admit what he had done.

Despite her increasing doubt, she told the rest of the team what she had seen on Sian Foster’s file at the hospital the previous evening. The more she’d thought over it, the more unlikely it had become. Kathleen. It was just a name, surely.

‘It could just be a coincidence,’ she said.

‘It’s not that common a name, though.’ Chloe stared at the board behind Alex, perusing the gaps that showed a lack of connections between the faces staring back at her. Sian Foster had now been added, alongside Gavin Jones. Other than being in a relationship with Gavin, it was unclear where Sian might come into any of this.

‘Was someone trying to leave us a clue through that song?’ Jake asked. ‘Literally naming a suspect?’

Alex shook her head. ‘I don’t think so. The sound was very unclear before the recording was enhanced, and the call was cut short not long after it started. Unless we’re way off the mark here, Sian Foster is a victim. She has no links to these cases other than being Gavin Jones’s girlfriend, and at the moment his alibis are solid. I think Chloe’s theory that it’s a ringtone is probably our best one.’

‘Bit of a weird coincidence, though,’ Dan said.

Alex nodded in agreement. ‘Are there any updates on Syed Hassan’s laptop?’

‘Two Hallowe’en outfits purchased online,’ Dan told her. ‘Neither of them a skeleton.’

Alex pursed her lips. She had been hoping for a result there, despite the fact that Youssef Hassan had now admitted to the arson at the shop. The other three attacks were linked, she was convinced of it. What she still wasn’t sure of was that they were carried out by the same person.

‘We don’t know that Syed and Jameel didn’t carry out the attack against Gavin Jones,’ Chloe said. ‘Could the outfits have been bought for that?’

‘Good possibility. Bit old for trick-or-treating, aren’t they? Gavin doesn’t want to make a statement, though, and we’ve got no evidence. We can’t take it any further.’

A silence fell over the room. The lack of progress was making everyone frustrated, and the more time that passed, the more the faces on the evidence board seemed to loom over the team, watching each and every one of them accusingly. It was 2 November, just three days until Bonfire Night. They were anticipating another incident that weekend. How many more names might be added to the board? Alex wondered. How many more innocent victims would fall prey to this murderer?

‘This has all the markings of a killing spree,’ she said, thinking aloud. ‘Gary Peters on Thursday, an attempt on Corey Davies on Saturday, Doris Adams Tuesday. There’s a regular gap between each crime and each attack has occurred in quick succession. We’ve been concentrating our focus on these faces,’ she said, passing a hand across the images of Jameel and Syed Hassan, before resting it on Gavin Jones. ‘But what if we’ve got it wrong?’

‘What do you mean?’

‘We’ve spoken before about the fact that our attacker preys on the vulnerable. Victims who are unable or unlikely to defend themselves.’ She returned the team’s attention to the board. ‘These are all grown men, young and strong. It didn’t need strength to kill Gary Peters, nor Doris Adams.’

She moved away from the board and ran a hand through her dark hair, pushing it back from her face. She wished she could give them more – that she was able to say ‘this is who we’re looking for’ – but they just didn’t have the details needed.

She turned back to the montage of photographs pinned on the board, stopping at the image captured on the CCTV of the bus that had picked up their skeleton figure.

‘This,’ she said, tracing a finger over the image before moving it to the close-up of the boot print that had been left on Doris Adams’s body, ‘doesn’t seem to add up with this. The driver guessed the man in the skeleton outfit to be around five foot nine. This boot print is a size six.’

She stepped back from the board and folded her arms across her chest.

‘We’ve already considered the possibility that we may be looking at two suspects here – one responsible for the deaths of Gary Peters and Doris Adams and the other for the attack on Corey Davies.’

‘So they’re not working together?’ Dan asked.

‘Not necessarily. They could be. It may be that the two of them were together for the first and last attack, but not for the incident involving Corey. Jake, what size are your feet?’

‘Eight. Why?’

‘Dan?’

‘Size nine. What are you thinking?’

‘I’m thinking one of our killers is a woman.’

They were interrupted by a man in uniform entering the room.

‘DI King,’ the officer said. ‘Gavin Jones has been found dead.’