I reach the entrance just as a woman in jeans and a shiny green bomber jacket is backing out of the door with a pushchair in tow. I hold it open for her and then slip inside. On the left wall is a bank of mailboxes, stairs on the right. I work out from the address Roemers gave me and the number of mailboxes that Huisman’s flat is most likely on the top floor, a calculation that turns out to be correct.

It’s number twenty, at the end of a corridor under a light which isn’t working. The doorbell doesn’t rouse anyone, and knocking doesn’t either. I try the handle gently, but the door’s locked. I’m just thinking that once upon a time this would have been easier. I could have simply kicked the thing in and claimed I’d heard a scream or a cry for help. I check the door sill, running my finger along just in case he’s left a key. All I get is a thick layer of dust obscuring the swirl of my fingerprint. Once again I think a well-aimed kick will sort it just as I think I hear something for real. I put my ear to the door and listen. There it is again: a faint noise I can’t quite make out. It’s like fabric moving. Maybe Huisman is in there and trying to hide behind the curtains? I kneel down and try to peer through the keyhole. It’s dark, though, so I pull out my phone and hit the torch app. It’s tricky to line up, and I’m struggling to get the angle right, which is maybe why I don’t see or hear them coming until it’s too late. I sense a presence and turn just as they see me. They stop dead.

‘Sir, what are you doing here?’ Jansen asks.

‘What he’s doing is sticking his nose in where it’s not needed,’ Vermeer says, walking swiftly towards me.

I put my finger to my lips, pointing to the door.

The look on Vermeer’s face is anger, but she stops and beckons me to her.

‘No one answered, but I heard a noise in there,’ I whisper to her when I’m level.

‘Okay, you go downstairs and wait –’

‘I –’

‘Downstairs. Wait,’ she hisses at me.

Turns out it’s not for that long.

And they don’t come down with Huisman, or anyone else. Vermeer spots me sitting on a low concrete wall, the surface of which is layered with the work of generations of young taggers practising their craft. Her phone goes off before she gets to me.

‘Wait,’ she tells me, answering her phone and walking out of earshot.

Jansen walks past awkwardly.

‘Huisman in?’ I call out to him.

‘Hasn’t been seen for several days, sir. At least according to the neighbours.’

‘Let me guess, since Kleine was killed?’