If our weight diminished as we gained distance from the swallower, I felt no benefit from it. In fact, the effective effort increased with our ascent, as my muscles grew ever more fatigued. But we stopped periodically, and when I had recovered some energy Jastrabarsk used the scratchy, failing squawk to ask if I wished someone to take over my burden.

‘There’ll be no loss of your share, Arafura. You’ve done well enough for a first-timer.’

‘I’m all right,’ I said, between heavy breaths.

As we got higher, though – taking longer than Jastrabarsk liked – even the Assessors began to paw through the hoppers and nets and tossed the occasional heavy item back down the staircase. We risked leaning over the edge, watching rejected trinkets hurtle into the airless depths.

‘Wouldn’t it be better to leave them on the stairs, for someone else to find?’ I asked. ‘They must have had some value, or we wouldn’t have carried them this far.’

They laughed at me.

The attrition of our suits continued apace, but it was following a predictable progression and no one seemed greatly troubled. The squawk became unusable unless we were almost helmet to helmet – and then it was easier to touch the helmets together and rely on the transmission of sound through metal and glass. Our torches faltered so that we were climbing in an ever-dwindling pool of light.

It wasn’t too bad. The less light we had, the less obvious it was that we were tiny little creatures winding our way up the inside of a vertical shaft, following the scratching line of a staircase. I kept as close to the outer wall as I could, and when I was there it was almost possible to forget that the staircase had an unprotected drop on the other side.

Finally – when it felt as if we had climbed twice as far up as we had gone down – we came to a landmark, a stretch of ten or twelve steps where the staircase had been damaged, three-quarters of it bitten away by some ancient violence, so that we had to squeeze into a single file and edge along with our backs to the wall. I’d detested that section on our descent but now I took some reassurance that we weren’t too far from the surface.

Our lights were nearly gone by then. That was when Prozor looked me hard in the faceplate, and although I was certain that my own torch had stopped working several turns of the staircase below, a yellow-green glow cast itself across Prozor’s helmet.

‘I thought you were keeping something back,’ she said, clanking her helmet against mine.

‘Keeping what back?’