I think back to the day I’d visited him. I hadn’t recognized him. The injuries and the panic attack I’d had made sure of that. More bits fall into place. Rein Benner disappeared after the DH Biotech trial. He must have changed his identity to Sander Klaasen then. More stuff: Klaasen had no background, he’d been like a ghost, we couldn’t find anything on him at all. Fits in with Benner’s disappearance. So what next? Klaasen kills Lucie Muller but I catch him. He goes to prison. But he beats someone into a pulp and then takes their place. I think of what the artist had said. Benner was good at imitating people, mimicking their posture. And the reason there’s been a gap between Lucie Muller’s death and Marianne Kleine’s is that Klaasen probably got out of prison recently and decided to carry on with his plan.

I lay it out for Vermeer.

‘Wait, hang on. How could he have taken someone’s place? Surely it would have been noticed?’

But would it? Prison guards have a lot to deal with, prisoners transferring in and out all the time. If Klaasen was smart there might be a way.

I get the prison warden I’d spoken to earlier on the phone.

‘Who was the prisoner who fought with Klaasen the day he was transferred to prison?’

The warden says he’ll check and tells me to hold. We sit in the car in silence. Vermeer seems agitated. I don’t blame her.

‘The prisoner was called Klaas Blok,’ the warden says when he comes back on the line.

‘Has he been released recently?’

‘Yeah, he was only in for seven years. Released two months ago.’

I hang up and am relaying this to Vermeer as a uniform knocks a knuckle on the window next to me. It makes me jump.

‘Beving wants you both upstairs, now.’

We get out and I run it through in my head again, testing it, trying to see any faults. At first I’d thought pulling a switch like that, in a high-security prison, would be impossible. But the more I think about it, the more I realize it could just happen. In the end they’re all just prisoners to the guards, maybe someone wasn’t paying attention that day? And if he had pulled it off … Still seems unlikely.

There are two uniforms by the door, as if there’s a prisoner inside. Beving himself opens the door as we approach.

‘Follow me.’

‘We’ve got something,’ I tell him. ‘We –’

‘Not now,’ he snaps. ‘Just follow me. You two as well,’ he says to the uniforms.

My phone starts ringing.

‘Inspector Rykel? I’m leading the team looking for the man who torched your boat. Think I’ve got a possible suspect so wanted to come back to you straight away.’

‘I’m listening.’