He was lying on the ground with blood all around him. I went up to him and I touched him, but I could tell he was dead. His eyes were open and he wasn’t breathing. Leon shuddered at the memory. I don’t even know what I was thinking, but I picked up the knife and I cut myself. I was trying to stop the bleeding when I turned around, and Miss Marcek was standing there. She looked at Mr Wilkinson, then at me, and I knew it must have looked like I killed him. So, I ran. He shrugged. What else could I do? I didn’t want her to blame it on me just because she’d seen me there.

‘Did you wonder why she was there? She hadn’t come with you on the trip.’

I didn’t even think about that straight away, he replied, shaking his head as if he was annoyed with himself. Then when I did finally realise, I knew she must have been the one who killed him, but I still couldn’t go to the police. I know what people think about kids who are in care, that we’re all rough and just make trouble. And after what I did to my dad, who would you have believed – me or her?

The detectives didn’t answer, and I knew what they were thinking. They each liked to think they would have listened to Leon, but when faced with the plausible explanations the deputy head would have come up with, would they have believed him?

I went to Samira’s house, because I knew she’d hide me without asking too many questions, he continued. She was scared, but I told her it’d be okay. Her parents are away and her brother is never at home. It was actually pretty fun, he said wistfully. But I thought the police would solve it quickly and I could come home.

‘I’m sorry it took us so long,’ Singh replied, and I could see from his face that he meant it.

I think Miss Marcek worked out where I was when she saw Samira call me on the day Mr Achembe was killed. Leon grimaced. Samira was really scared, I don’t think she noticed Miss Marcek was behind her when we were on video chat.

I remembered Liz walking down the drive towards me. At the time, I’d assumed she’d been up to check the road, but really she must have been arriving back after kidnapping Leon from Samira’s house. There had been plenty of time for her to slip away while the police were interviewing other staff members. The snow had been so bad by the time she returned, though, she wouldn’t have been able to get her car all the way to the school. She must have abandoned it and walked the rest of the way.