So they measured the volume of the Hatch and its emplacement directly, from the displacement of the lubricant fluid. She had them repeat the measurement a few times for accuracy.

The direct measurement differed from the result obtained by multiplying together length, breadth and height.

‘It’s too big,’ Trant said, wondering. ‘Ten per cent or more . . . Too big for any errors.’

‘I don’t understand,’ King said, grumbling. ‘I can’t get my head around this. All this mucking about with engine oil!’

Stef grinned. He seemed disappointed she hadn’t ordered some vast super-physics experiment to be run. ‘Sir Michael, it’s as if you have a one-litre jug, only it holds two litres.’

‘It’s bigger on the inside than the outside?’

‘Something like that. There’s some kind of distortion of space-time going on here.’ The dome had been cleared away now, the Hatch revealed again, the last of the lubricant fluid removed. Stef knelt and touched the panel surface once more.

Trant was staring past her. ‘Major—’

Stef passed her hand over the edge. ‘Just like before, I feel something, like a tidal effect.’

‘Major Kalinski, I think—’

‘And just as the kernels are evidently some kind of space-time phenomenon, so is the Hatch—’

‘Stephanie!’ King snapped.

Stef was startled into silence, and turned. Just for a moment King had sounded like Stef’s father, as King had surely intended.

Trant, glaring, was pointing at the Hatch. ‘Shut up,’ she said evenly. ‘Turn around. And look.’

Stef turned, needles of icy anticipation prickling along her spine.

The Hatch had changed.

That smooth surface, within the circular seam, was smooth no more. A series of indentations had appeared, set evenly around the edge – they came in pairs, twelve pairs, she counted quickly, like the numbers on an antique clock dial. The indentations themselves were complex in shape, with a textured central crater, and five channels running off in a lopsided star shape.

‘Hands,’ King said. ‘They’re meant for human hands.’

Stef saw it as soon as he said it. Somehow she’d been blinded by the obvious, by the incongruity of the setting.

‘The imprints of human hands,’ Trant said slowly. ‘On an artefact that’s nearly as old as Mercury itself. That’s been here forty thousand times as long as humanity has even existed.’

‘More to the point,’ King said, ‘imprints that weren’t there a minute ago. Not before Major Kalinski ran her experiment with the lubricant.’

‘And,’ Stef said carefully, ‘before we made our very first deduction about it. Suddenly it knows we are here.’

Trant guffawed. ‘It knows? Now who’s hypothesising about agencies?’

Stef ignored her. ‘The purpose seems obvious.’ She stepped up to the Hatch, and knelt beside it once more. She held out her hands, and again felt that odd tidal ripple. Had the quality of that sensation changed at all? Her senses didn’t seem subtle enough to be able to tell. She looked back at King and Trant, at the technicians and guards behind them, all in their ISF pressure suits, like so many robots. All of them staring straight back at her. As if daring her.

She turned, spread her gloved fingers, and extended her hands so they were over one of the indentation sets. But she held back from touching the surface. Should she do this? The Hatch had changed, it seemed, the minute she had figured out something about its true nature. It had responded. How would it respond, what would change, if she went one step further now?

Only one way to find out. Oddly she wasn’t afraid any more.

She settled her hands into the indentations. Gloved, they seemed to fit perfectly.

And the Hatch immediately began to open.

Trant grabbed her shoulders and pulled her back, bodily lifting her in the low gravity.

They stood and watched as the huge circular plate lifted out of its seam, attached to the emplacement by some invisible hinge – how was it being held? Stef bent to see. The rising lid just touched the wider emplacement at its rim. There seemed no material attachment.

And again she’d had her eye off the ball; she wasn’t observing the most striking phenomenon. Under the rising Hatch was revealed a chamber, cylindrical, maybe four metres deep, set in the Mercury rock. It seemed to be made of the same greyish substance as the rest of the installation, and it was lit by a sourceless glow.

‘That’s impossible,’ King said.

‘You are right,’ said Monica Trant. ‘There’s nothing but rock under that plate. We measured it.’

But Stef could see the glow coming from the impossible pit reflected in their visors, their staring faces, baffled. She felt a peculiar exhilaration. This wasn’t like her at all. Most of her life, her science, had proceeded in cautious, methodical steps, with each new extension of her knowledge building incrementally on what had gone before. Now all that was thrown out; now she was rushing headlong into the unknown, the non-categorisable, the unidentifiable, in a way she’d never imagined.

This wasn’t Stef Kalinski’s way. She was thrilled. She could barely wait for the next step.

As soon as the Hatch lid had come to a halt, standing vertically from its invisible hinge, Stef walked forward to the edge. ‘Monica. Give me a hand.’

‘You’re going in there?’ Trant glanced at King, who shrugged. Trant said, ‘I don’t know how wise this is.’

‘We’ve come this far. It’s obvious what we’re meant to do next. We can’t stop now.’ Stef glanced up at the rig of cameras and sensors all around the emplacement. ‘We’re being recorded, right? Whatever happens, those who follow us will know what became of us.’

‘Yes. But this doesn’t seem too scientific, Stef. Just to plunge in.’

‘This isn’t science. This is exploration.’

‘No,’ King gloated. ‘Let’s be honest. It’s appropriation. It’s conquest. It’s going to kill those gerontocrats in New Beijing, when they read about this day, when the security blankets are lifted in fifty or a hundred years’ time, that we haven’t just got the kernels – now we have this.’

‘Whatever. Let’s get on with it.’ And she held out her arms.

The ISF goons came forward to help too. They braced Trant while she took Stef’s gloved hands in her own, and lowered her into the pit. Stef made them move slowly, while she tried to be hyperaware of any odd sensations, any more of those tidal effects. She felt nothing untoward. It was just a hole in the ground, impossible or not.

When they had lowered her as far as they could they released her hands. Gentle as a snowflake she settled to the floor. She looked up at the opening above her, the circle of visored faces peering in.

Then she turned around slowly, inspecting the walls. ‘There’s another hatch,’ she said. ‘Another circular seam. Set in this wall. Smaller than the big one up there, but here it is. And, guess what? It has handprint indentations again.’

King called down, ‘Major, maybe you’ve gone far enough.’

‘You’re kidding,’ she said, staring at the hatch, raising her hands. ‘What would you do, if you were down here?’

‘Think about it. Maybe any curious, tool-wielding species would react the same way to this set-up. You’d go in, one step after another.’

‘You mean—’

‘Maybe it’s a trap.’

‘And maybe it isn’t,’ Stef said, unmoved.

‘We aren’t going to stop her, sir,’ Trant said. ‘Stef. You might get cut off. Keep talking to us. All right?’

‘I hear you. Here I go, with a handprint lock once again.’ She settled her hands into the indentations at twelve o’clock on the wall before her. ‘It’s opening . . .’ She had to step back smartly as the curved door swung back, as smoothly as the hatch lid itself. ‘Again, I can’t see a hinge, nothing material attaching door to wall. There’s another chamber beyond. A second chamber, similar to the first in dimension. More of those grey walls, the sourceless light.’ She stepped forward cautiously, towards the doorway rim. ‘And . . .’