Strambli carried on with her probes and boxes for longer than was comfortable. She was sliding a metal disc around on the periphery of the door, the disc connected back to her helmet while she drummed on other parts of the door with her fingers. Sometimes through the grilled-over window of her faceplate I could see her squinting hard with the concentration, only making those two eyes of hers look more mismatched.

‘What I’m saying, is . . .’ Prozor started.

‘What you’re saying is, you think you know better than the Queenie’s regular Opener. That’s what it is, isn’t it?’

By now even Trusko was getting impatient with Strambli’s leisurely concept of progress.

‘Perhaps if Prozor has something to contribute . . .’

I had something to contribute, too. We had sixteen hours left before the surface bottled us in like pickled specimens. The way Strambli was going about it, we’d need all sixteen to crack this one door.

‘Get it off your chest then,’ Strambli said.

‘The locking mechanism’s standard enough,’ Prozor said. ‘You can crack that easily, with the right shunts and magnetics. You figured that out fast, I know. What’s throwin’ you is that the anti-tamper circuit’s cross-wired compared to most of the doors you’ll have run into or read about in books. So your inductance coils are playin’ off the wrong polarity to begin with. Flip ’em; reverse that diagram in your head, and you’ll be in and through in no time. And watch for a mercury trip on the secondary latch.’

‘There’s no mercury trip.’

‘What if you assume there is, and then I’ll apologise later when you prove me wrong?’

Strambli said something under her breath, but with Trusko breathing down her neck, now wasn’t the time to get into a squabble with Prozor. Huffing out her disapproval, she rearranged her equipment and got us through the door inside ten minutes.

One by one we crossed the connecting bridge, until we were standing on the firm ground of the bauble, with the bucket waiting to take us back up again. Those two gees were beginning to grind me down. I could see why Trusko had thought better of roping in Drozna, who weighed twice as much as the rest of us to start with.

The door had gone sideways into a wall. Facing us, leading horizontally away from the main shaft, was a smooth, circular tunnel. We had to stoop just to walk down it, the tops of our helmets scraping on the ceiling if we weren’t careful.