I was in Samira’s room when Miss Marcek turned up, grabbed me and shoved me into her car, Leon continued. She threw my bag into a bush, but I’d dropped my phone in the hallway so she couldn’t get it, and say anything pretending to be me. When we got to her house she locked me in the summerhouse. I asked her why she didn’t just kill me, and she said she had to wait for the right time.

Singh had told me earlier that Liz Marcek had confessed to planning to kill Leon and pin all the murders on Cassie by faking a suicide, making her leave a note about what she’d done.

Why did she do it? Leon asked, his eyes wide. Why did she do all of this?

The detectives looked at each other, obviously wondering how much they could tell him, but Sasha got there first.

She blamed Mr Wilkinson for her brother’s death. Mr Achembe found some deleted messages she’d sent to Cassie and confronted her about it, so she killed him to stop him telling the police.

Leon nodded sadly, accepting this explanation. It would all be in the papers and online soon enough, so it made sense to at least tell him why he’d gone through such an ordeal.

We left the residence and went back over to the main building, where Jane Villiers was waiting for us in the head teacher’s office.

‘Now the case is solved I thought I could reclaim my old office,’ she explained.

‘Are you back for good?’ I asked.

‘The governors asked me to come in for now, as an interim head until the two management posts can be advertised. However, before that happens I think we’ll have a battle to keep the school open. I know there have already been some parents indicating that they will be sending their children elsewhere, and Ofsted will be paying us a visit very soon.’ She looked down at her old desk sadly. ‘Many times in the last few months I’ve wished to be back here, but I never would have wanted it at the expense of someone else’s life. Poor Saul. I was the one who got him involved. I feel responsible.’

‘You’re not responsible for anything Liz Marcek did,’ Singh said firmly. ‘She chose her own course of action, and nothing you did could have prevented it.’

‘If I’d been included in the interview process for my replacement, perhaps I could have,’ Jane countered.

‘I don’t think the death of Liz’s brother would have been something Steve Wilkinson advertised. She didn’t tell anyone else about it, so I doubt she would have told you either,’ Forest replied.

‘How did she do it?’ Jane asked. ‘Not the murders, but all the sneaking around? Getting Cassie involved, preying on the students like that.’