‘Little man,’ he said, as I thrashed like something dying in a bigger animal’s mouth, flailing at him with my legs. ‘Don’t you know that you should be on our side? Can’t you see that we’re doing the job you should be doing? Are you so stupid—’

I wrenched my right arm free and stuck my thumb in his left eye. Then I kept it there. He jerked away from me with a scream and then I was on my feet and trying to slam the sole of my right shoe into his knees, and I realised that I was trying to fight like Jackson Rose, going for his eyes and his knees, kicking him again and again, catching his shin and his calf muscle and his upper thigh, kicking him everywhere apart from his knee.

But he backed off with one hand over his eyes and I went after him, still kicking.

I took my breath and I took my aim.

And finally I caught him, my right foot striking him on the side of his knee, buckling the big man and making him roar like a wounded bear, swiping out at me with the blade in his right hand. I felt something sharp pass across my forehead and then it was warm and wet but there was no pain yet, and I realised he had cut me with his blade.

But he was done.

And so was I.

I sank to my knees, the blood flowing freely now, my hands covered with it as I tried to keep it from my eyes and Wozniak crumpled against the wall, moaning as he measured the damage. I stared at my hands, weak with the loss of blood and the paralysing shock of being cut. And when I looked up I saw him hobble through the crack in the wall of that secret room.

I must have gone after him because I was aware of passing down Dead Man’s Walk and into the broad, low-ceilinged tunnel that has waited beyond it for centuries.

I found the stone staircase that went deeper into the city and I took it, hearing Wozniak ahead of me, making the infuriated sounds of a wounded animal. We moved slowly. I looked at my phone once. But there was no signal down here. This was the past.

The stairs ended.

I called his name.

‘Wozniak! Wozniak!’

But he kept on and so I went after him, deeper into that other city, the forgotten city, the underground city, to where the stairs finally ended and there were four identical tunnels, each with a rounded arch, wide but not high, built to process large numbers of people who had been dead for nearly a hundred years.

And I reached the train station where two wooden platforms faced each other across the ancient tracks and where, on a big red circle, the name of the station was written in black letters on a white background.