The sixth-floor hallway was freezing. No lights anywhere except for the light under the door of 603. I dialled the landline and heard it ring inside. So I was at the right place, at least. No one answered. I knocked on the door, listened for movement on the other side. No sound.

I didn’t know who or what the apartment represented. I wasn’t quite ready to draw the attention of a break-in. Not unarmed.

On my way back down I spoke to the homeless family.

‘Have you seen anything strange recently? A woman?’ I tried various languages, got stares. ‘Know who lives in 603?’

‘One night,’ the father eventually said, in faltering Russian. ‘We stay here just tonight. Tomorrow we go.’

I needed to find a cathedral.

Black Mass was Joanna’s system, and she’d chosen the name. Her idea was that, even in an unfamiliar city, you could still communicate a location by code. So you had to think what landmarks a city might have: one code for general post office, one for town hall, one for cathedral.

The Assumption Cathedral in Astana was only five years old, though you wouldn’t have guessed it. White towers with narrow, prison-like windows supported blue and gold onion domes. A brass plaque announced that it had been funded by Gazprom. The towers looked a bit like distillation towers on a refinery.

The car park was empty, as was the security booth at its entrance. There were few surrounding windows, roofs or ledges with a sight onto the cathedral square. I couldn’t see much, but then nor would anyone watching. The cathedral was open. I went in, impressed at the sense of age they’d installed – the incense-darkened icons. I sat in a back pew, thawed out, breathed in.

It would do.

I sent the cathedral code to the TutaNota address, along with a number for my new mobile, then drove on. I should have settled in properly first, I thought, assessed security, familiarised myself with the terrain before trying to set up a meeting, but I didn’t know how long I had.

ELEVEN