Robin cranes his neck to try and see. It looks like a computer printout from a spreadsheet. Lines of text in columns.

‘It’s the event log from the BBC server at the university,’ Sophie says, and Robin feels a ripple of apprehension. ‘Where the video was stored.’

‘Why do you have this?’ Robin asks Sophie. ‘And, more to the point,’ he turns to Craig, ‘why don’t you?’

‘Our digital team checked that server,’ she snaps. ‘There was nothing there of use. The video files have gone.’

‘Yes,’ Sophie says, waggling the page in her face. ‘But this says who logged on and when. Don’t you want to know who deleted them?’

Craig snatches the page from Sophie’s hand.

‘And?’ Robin asks impatiently.

Craig looks up from the paper. She hands it to Robin, who scans the text. A login for CALLOI occurs first thing Wednesday morning. Then nobody else until WHITEJ logs on, on Wednesday night.

‘Ian Calloway,’ Sophie says smugly. ‘Have you spoken to him?’

‘Not since his statement last week,’ Craig replies. ‘But it makes sense he would delete the files. He’s Finn’s friend. He’s got rid of proof of the murder.’

‘That’s one theory,’ Robin says. ‘Sophie,’ he asks, turning to her. ‘With Sharp dead and Finn in prison, who would get proprietary rights to the Doppler?’

‘Well, the university, essentially. They own everything.’

‘So there’s no money as motive—’ Craig begins, but Sophie interrupts her.

‘That doesn’t matter. You don’t work in academia for money. You do it for professional recognition, to be at the top of your field. And someone would have to publish the findings. Take the glory. And that would probably be Ian now.’

Sophie frowns. ‘I’ve never liked Ian. I thought he was jealous of Finn, but Finn always said I was being silly. But when I saw him last week, it felt like he was enjoying all this. Enjoying the fact that, with Finn out of the way, he was in charge.’

Robin smiles weakly at Sophie. He was wrong about her. She is passionate and impulsive, but that has worked in their favour in this case. She came through for Finn, which was more than he’s achieved.

But it’s too late. ‘So Calloway deleted the videos,’ Robin sighs.

‘No,’ Sophie says, frustrated. ‘This is what I’ve been trying to tell you. This shows he didn’t just delete the files.’

She leans over and points to a line on the piece of paper, the server log that Robin’s still holding.

19/05/21 09:25:54, Copied, it says, then a letter: an external drive.

And below it: 19/05/21 09:25:58, Deleted.

Sophie looks up at Robin. ‘He copied them first,’ she says. ‘He might still have them.’

Robin turns quickly to Craig. The look on her face is something between humiliation and anger. She’s screwed up, and she knows it.

But she turns to her DC, galvanised into action.