Singh looked at them. ‘If I find out that any of you are hiding something that could help us find Leon, or find out who killed Mr Wilkinson, we’ll be having a very serious conversation about wasting police time. Do you understand?’

The three of them nodded, but none of them volunteered any new information, so Liz allowed Bradley and Courtney to go back to bed.

Cassie, you wait a minute, the police want to speak to you.

Come on Miss Marcek, she knows what she did was wrong, Courtney said. Can’t it wait until tomorrow?

Absolutely not. You’ve got Paige and DS Singh out of bed in the middle of the night, Cassie. The least you can do is sit here for ten more minutes.

She shooed the other two back to their rooms, watching as Bradley climbed the stairs. It looked like he was going to try and sign something to Cassie behind our backs, but then he noticed me watching him and he carried on up.

‘Cassie, why did you think your phone might be in Mr Wilkinson’s office?’ Singh asked once the other two students had gone.

The girl sat with her hands between her knees, watching us. She shrugged, but didn’t offer any other response.

‘Cassie, I’d like you to answer the question.’

Someone told me it would be there.

‘Who told you that?’

She shook her head. Just someone.

‘Was it another student?’

No response.

‘Or an adult?’

Again, no response from Cassie.

Singh sat back in his chair and thought for a moment. ‘Is there a reason you decided to go and look in the middle of the night?’

Cassie looked up at Singh, her eyes wide. They said I had to go at midnight, then nobody would see me.

Singh gave her a sympathetic smile. ‘Do you think someone might be trying to get you into trouble, Cassie?’

The girl was taken aback at this question, and looked to Liz before she answered.

No, they wouldn’t want that. They wouldn’t want me to get into trouble.

‘They told you to go and look in a locked room in the middle of the night. They probably knew the alarm was going to set off and the police would come. Maybe they thought it would be funny to get you into trouble. Did they give you the key?’

Cassie shook her head, but the hurt in her eyes showed she believed what Singh was saying was at least possible.

‘That sort of person isn’t worth protecting,’ Singh said gently.

For a moment, I thought Cassie was going to tell him the truth, but she shook her head. I can’t remember who it was, she signed, not making eye contact. I must have misunderstood them. It’s my fault.

Singh tried a few different ways to persuade Cassie to talk, but all to no avail. Eventually, Liz sent her off to bed.