The whole team assembled that morning in the central incident room. The place had been a buzzing hive of rumour, news of the incident involving Leah Cross and Isobel Matthews having filtered through the station.

‘Right,’ Alex said, bringing the murmur of whispers and gossip to a hush. ‘Quite a lot to go through this morning, as I’m sure you’re all now well aware. Leah Cross has been found, though not under the kind of circumstances any of us might have anticipated. There are probably various versions of the incident doing the rounds, so let me put you all straight on what happened last night. Leah Cross went to a house on Broadway yesterday evening, having received a text message from the pay-as-you-go mobile phone Leighton used to contact her with. The house is one of Leighton’s rental properties, so she went there thinking she was going to meet with him, presumably to discuss what happened when he was here talking to us about the hit-and-run. When she got to the house, it wasn’t Leighton she found there but his daughter, Isobel.’

She gestured to a new photograph that had been pinned to the gallery of faces: a pretty young blonde woman, a younger version of Melissa Matthews.

‘Isobel Matthews is twenty years old, just a few months older than Leah Cross. We now know that in the summer of 1996, Leighton had a two-week affair with a woman called Carol Chambers, who he met during a trip to Cornwall. A writing retreat, apparently,’ she added, eyebrows raised. ‘The result of that affair,’ she traced her finger to the photograph of Leah Cross, ‘was this young lady. We have yet to find out the details of how Leah discovered her father’s whereabouts, but it seems increasingly apparent that her doing so was the catalyst for a number of incidents that followed, the most significant being the death of Keira North.’

Chloe caught Alex’s eye and offered her an encouraging smile.

‘Leah Cross, as we all know, is a compulsive liar, yet she’s made an allegation against Isobel Matthews that might hold some weight. She claims it was Isobel driving the car that hit her. We know Leighton Matthews has been lying to protect someone, and until now we’d all assumed that someone to be his wife. What if he’s been lying to protect his daughter? If Isobel made the same assumption we did and believed Leah to be having an affair with her father, Chloe’s theory of mistaken identity becomes even more of a possibility. It seems entirely plausible Isobel might have gone to that party with the intention of confronting Leah. Was last night an attempt to correct the mistake she’d made? We need to speak again to these people,’ Alex swept a hand across the array of faces surrounding the people who remained central to the investigation, ‘and see if we can get anyone to identify Isobel Matthews as having been at the party that evening.’

‘So Isobel Matthews pushes Keira thinking she’s Leah,’ Dan said.

Alex nodded. ‘That’s the theory at the moment. As soon as news of Keira’s death hit the press, Isobel would have realised her mistake. This could have had a number of effects – she might have felt guilt at what she’d done to Keira, but equally she may have been angry that Leah had walked away from it all. It could have been a mixture of both. Perhaps she thought it was Leah’s fault that Keira died, not hers.’

‘So she stabs Leah after failing to kill her with the car,’ DC Jake Sullivan said.

‘Did she, though?’ Alex questioned. ‘I don’t believe it for a second. Last night, Isobel Matthews was in such a state we were unable to speak with her for long. She was a bloody mess according to the first officers who attended the scene. Leah claims to have attacked Isobel after Isobel stabbed her. Really? She managed to beat the girl black and blue having just been stabbed in the stomach?’

‘So what are you suggesting?’ DC Daniel Mason asked. ‘Leah beat her up first and Isobel stabbed her in self-defence?’

‘More likely,’ Alex said. ‘We need to speak with Melissa again, see if she sticks with her recently changed version of events. If Leighton’s covering for Isobel, it’s likely Melissa will know about it.’

‘And neither woman knows yet that Leah is Leighton’s daughter?’ one of the other DCs asked.

Alex shook her head. ‘So far we’ve given him room to break that news himself. He’s obviously still reluctant to, so perhaps we’ll have to do it for him.’

‘How did Isobel Matthews know about Leah?’ Dan asked. ‘I mean, there must have been something to link Leighton to her, or vice versa.’

‘Something else we need to find out,’ Alex said. ‘These theories remain just that until we find proof. We also need to consider where Tom Stoddard comes into all this. There’s the drug dealing to bear in mind. In his interview with us, Tom claimed Leah was involved in the dealing. Did she kill him to keep him quiet and keep herself out of trouble?

‘Chloe, we’re going back to the hospital to speak with Leah. Dan, I’d like you to pay another visit to Melissa Matthews this morning. The rest of you, we need to speak again with people we know were at the party that night. Let’s see if we can get an ID on Isobel Matthews. And keep working your way through this CCTV, please – I know it’s tedious, but perhaps now we have another face to look for, we might be able to find it. The footage from outside the shop on Railway Terrace might have picked up Isobel on the night of the party.’

She glanced at Harry Blake, who had been watching her throughout. ‘Let’s not forget that whatever else Leah Cross might have got away with so far, Amy Barker has identified her as having sold her the drugs at Fusion nightclub the Monday before last. It’s not enough to secure a conviction, so let’s make sure we find something else.’