Despite Robin’s protest, Craig insisted on them taking Grey’s car, and having someone else drive him puts him on edge. Especially DC Grey: he’s serious, face forward, concentrating intently on the road. It seems to Robin that he’s only just passed his driving test, leaning forward slightly as he drives, and the broken exchange distracts Robin for a moment, if nothing else. It soon transpires that DC Grey had been a civilian analyst for the force for a couple of years, eventually training and transferring into uniform, before becoming a detective. From the look of him, he can’t be much older than his late twenties, with a chin that barely needs shaving and delicate, almost androgynous, features.

‘What’s your first name?’ Robin asks, trying to conjure up some familiarity.

‘Kennedy.’

‘What, sorry?’

Grey chances a look at Robin. ‘Kennedy.’

‘That’s your first name?’

‘Yes.’

‘Anyone call you Ken?’

‘No.’

They lapse back into silence. Grey it is, then.

‘What’s DI Craig like to work for?’

‘Good.’ They pull up in the car park of the university, and Grey looks across at Robin. ‘She’s smart, Sarge. I know she’ll do what’s right.’

To secure a conviction, or what’s right for Finn? Robin’s not sure.

The two of them head towards Finn’s lab, with Robin leading the way. He had a tour years ago, when Finn was doing his PhD, and knows he hasn’t moved locations since.

A tall, well-built man waits in the doorway, standing up straight when he sees them approaching. He looks older than DC Grey and holds out his hand when they’re near.

‘Ian Calloway,’ he says. ‘One of Dr Mason’s PhD students.’

Grey introduces himself, showing his ID. ‘And this is… Robin Butler.’

Robin glances at Grey, then shakes hands with Calloway. So that’s how it’s going to be, he thinks. No police credentials at all? But he stays quiet, accepting his fate.

‘We haven’t got much time,’ Grey continues. ‘Could you show us what Dr Mason was working on? Some sort of equipment they were trialling?’

‘Yes,’ Ian says as they walk. He escorts them through the electronic security doors into the lab. ‘It’s a dual polarisation Doppler. Basically, a high-resolution radar that scans the atmosphere and tells us what’s up there. The party trick of this guy is that it can measure wind speed and direction, as well as tell the difference between hail and rain and other debris.’ He stops next to two large white satellite dishes attached to an array of electronics. ‘This is one of our prototypes. Bistatic, operating at 94 gigahertz. We’ve used it before, but only in experimental settings. We were all excited to see it play out in a real storm, especially one of Tuesday’s magnitude.’

‘But Doppler radar has been around for some time,’ Grey points out. ‘What makes this one special?’