‘Did it never occur to you that Leon’s disappearance could have something to do with Joe?’

The girl’s eyes filled with tears. I told him not to bother with online relationships, that nobody knows who anyone really is, and I thought he’d stopped. He told me he was going to stop chatting to Joe.

‘When did he tell you this?’

About a week ago. I thought he’d actually listened to me for once, but he obviously just lied to me so I’d stop nagging him. A tear rolled down Samira’s cheek and she wiped it away aggressively. Who is he?

‘Joe? We don’t know, but we’re doing our best to find out.’

She thumped the wall, then turned and stormed out. For a moment I thought Sasha was going to go after her, but then she sat down in her seat again and shook her head.

I hadn’t realised they were all keeping such big secrets, she told Singh, and I could see that she was blaming herself.

‘You said it yourself, teenagers keep secrets,’ Singh replied. ‘We can’t force them to tell us what they know, especially when we don’t know what it is they might be hiding. Perhaps I should speak to Miss Marcek about an assembly for all the students, about online safety. It’s possible other students are behaving in the same way as Leon.’

I thought back to what Anna had told me about past safeguarding issues, and I wondered if they had been connected to the students’ online behaviour. Should I ask Sasha what she knew? I considered it, but then decided not to. I didn’t want to throw the cat among the pigeons and confuse the investigation with information that could be completely irrelevant. It’d have to wait until Anna and I had visited Jane Villiers this afternoon.

Singh spoke to Courtney next, but she completely denied having heard of Joe or knowing anything about what Leon had been planning. I knew she was lying, at least about the first part, but there was no way to prove it. Singh dismissed her with a rueful shake of his head, then ushered Cassie inside.

How would I know who Leon had been talking to? she asked, her eyes bright. He never talked to me about anything.

‘We have reason to believe you knew about Joe, along with Courtney, Bradley and Kian.’

Did they tell you that? Why would they tell you that? I haven’t been talking to anyone called Joe.

Singh frowned. ‘I didn’t say you’d been talking to him, just Leon.’

Cassie paused. Whatever. I don’t know who Joe is or why he’s interested in Leon.

‘The other day you told us you knew things about Leon that nobody else knew. I want you to tell me what it is you know, Cassie.’