STAFF ONLY, said a door, and I went through it. It was a long corridor with offices on one side. I walked past the offices, looking in, seeing that they were quite small, glimpsing screen savers on computers and the remains of café-bought lunches eaten at the desk, seeing the faces of all those office workers weary with mid-afternoon torpor. Everyone ignored me. There was an unmarked door at the end of the offices. It was unlocked so I went through that, too, and down a staircase, deep into the bowels of the building. I could hear machinery rumbling and wheezing, like the engine room of some old ocean liner. I came to an ancient boiler room.

This basement area was bathed in a weary green light. There was an unmarked door at the end of the corridor. It was locked.

‘Are you all right?’

I turned to face Andrej Wozniak.

‘I just want to check something out,’ I told the bailiff. ‘Do you have a key for this door?’

‘I can find you one.’

‘Thanks.’

He was back within minutes. I stood aside as he unlocked the door for me and I went through, descending another flight of stairs. There was no light now apart from what seeped down from the boiler room. It was colder down here, and getting darker by the second as I continued down the stairs, and I could feel the weight of the city was pressing down on me. Wozniak’s footsteps were right behind me.

I stepped into a room that was abandoned years ago.

‘What’s down here?’ I said.

‘Storage rooms,’ said Wozniak. ‘But there’s a lot of damp so we can’t keep papers down here. They rot.’

I walked on. There was empty room after empty room, the damp showing through the cracked and peeling plaster.

And then I opened a rotten wooden door and finally there was a room that I recognised.

A room with white tiles that had turned green with time.

A room that was shaped like a cube.

You could smell the decay.

‘You having any luck?’ Wozniak said.

I thought he was talking about Mrs Goddard.

‘They gave the boy leave to appeal his conviction,’ I said. ‘They said it wasn’t joint enterprise.’

‘I meant the other thing,’ he said. ‘Your murder investigation. Any luck with that?’

It was like a room that I had seen in a dream. Everything felt slightly changed from what it should be. There was no kitchen step stool. The stool where they had stood Mahmud Irani. And Hector Welles. And Darren Donovan. And me.

It was not dark. A green light ebbed into the room from the boiler room a floor above. My eyes scanned the floor.

There was no gun.

And there was no rope hanging from the ceiling.

And so I was wrong. This could not be the place.

I was overthinking it. I was trying too hard.