‘You don’t know of anyone else your son might have been involved with?’ Adrian asked.

‘No, I’m sorry.’

‘If you hear from him, or if you think of anything else, then give me a call.’ Imogen handed her card to Judith Beacham.

‘Is he in a lot of trouble?’ she said, a hint of defeat in her voice – as though she already knew the answer.

‘We just want to eliminate him from our enquiries.’ Imogen smiled, the stock reply when you didn’t want to give the game away.

In a way, it was the truth, it would be great to be able to take him out of the equation, but from what Judith Beacham had said about his escalating bad behaviour, it seemed entirely possible that he was involved. Was he involved enough to have killed Caitlin, though?

They had linked the pair together now, which was at least something. They still needed to find the person who assaulted Adrian. Adrian had been certain it wasn’t Russ Beacham and Imogen couldn’t imagine he would feign any kind of certainty if it wasn’t true, so that meant there was at least one other student involved.

Imogen and Adrian said goodbye to Ms Beacham and walked back to the car. The sky had clouded over since they had been inside the flat. Imogen found herself shivering; she still kept seeing Caitlin’s ashen face and she needed to get it out of her mind somehow. She couldn’t help feeling like they had failed her, even after what she had done.

She looked over at Adrian as she got in the car. His face was screwed up in a mixture of concentration and concern.

‘Thoughts?’ Imogen said.

‘He was in it, wasn’t he? Even the fact of the one-parent family unit makes him a slightly more vulnerable person.’

‘Hey! I was in a one-parent family.’

‘So was I for the most part. I’m not saying anything other than, in terms of vulnerability, that leaves him a little more open to manipulation.’

‘I suppose.’

‘Do you think Caitlin was part of the manipulation?’ Adrian said.

‘How do you mean?’

‘Beacham was an average-looking kid, Caitlin was not; maybe one of her tasks was to make Beacham fall for her. It certainly wouldn’t be out of character for her to use her looks to get someone to do what she wanted.’

‘I hadn’t thought of that. That would make sense,’ Imogen said, aware that Adrian was talking about himself.

‘See, I’m not just a pretty face,’ Adrian smiled.

‘So, they get Caitlin together with Beacham, maybe to control him somehow. Then they draw him in by telling him that she is going to get hurt in some way.’

Imogen could see quite plainly that Beacham and Caitlin were not evenly matched in terms of looks. He wouldn’t have ever had a relationship with someone like her before.

‘Do you think he found out the truth and killed her for it?’ Adrian asked.

‘It’s possible I suppose,’ Imogen said.