The dome itself was cluttered with white-box science and computing gear, and what looked like atmospheric control equipment of the kind he remembered from Mars. The interior seemed brilliantly clean to Yuri, even sterile, like a hospital. There was no need for artificial light under that huge lowering sun, but floods stood on tripods around the pit, into which cameras peered, presumably day and night. Colonel Kalinski, in her black-as-night astronaut uniform, was the only person here – her, and the four arrivals from Proxima Centauri.

Beth quailed from the brilliant sunlight overhead. And she threw up, suddenly, spewing the rich food she’d eaten in the substellar base half-digested onto the clean floor of the dome. Some kind of servo-robot, a more advanced model than Yuri had seen before, came scuttling out to scoop up the mess with quick vacuum sucks.

‘I’m sorry,’ Beth said, sounding distressed. She wiped her mouth with the back of her hand.

‘That’s OK,’ Kalinski said. ‘Do you need to clean up? We can give you fresh clothes from the stores, of course . . .’ She hesitated, listening to a comms unit at her ear. ‘My administrators are scrambling to put together some kind of response to this situation. For a start I’m to drive you over to the hab domes. I’m sorry to be disorganised, we’re not prepared for this, as you can imagine.’ Her accent sounded vaguely American, Yuri thought, but with a twang he couldn’t quite place.

Mardina said, ‘This must be strange for you too.’

‘Kind of. But the Hatch is the reason I’m here, on Mercury. I’m a theoretical physicist. Since the Hatch was uncovered, I’ve seen a lot of strangeness. Believe me, you four walking through from Proxima doesn’t even top the list.’ She grinned, somewhat ruefully, Yuri thought. ‘But I’m sure glad I was here to see this, to see you arrive. Once I saw the images of your Hatch on Prox c, matching the one here on Mercury, I knew it had to be something like this.’

Yuri frowned. ‘Like what?’

‘A lightspeed transit system. Like a subway. I mean, you got here at lightspeed, nearly, we established that already. A four-year transit time. With no subjective time lag at all – am I right?’

‘A lightspeed subway?’ Yuri asked. ‘Built by who? And why?’

Beth said now, ‘And I show up in the middle of this cosmic wonder and throw up all over it.’

Kalinski laughed and took Beth’s hand. ‘Don’t worry about it. Somehow it seems appropriate . . . You know, Beth Eden Jones, you’re the first human born on Proxima c to have returned to Earth. Think of that.’

Mardina grunted. ‘She’ll be famous.’

‘For better or worse, I think that’s true.’

Tollemache seemed to like the idea of that. ‘Famous, eh?’

‘Oh, yes. The images you sent back of the Hatch twin on Proxima c have been a sensation.’

Tollemache hefted his sensor pack. ‘Images taken with this very pack. Look, I need to speak to people.’ He thought it over. ‘My superior officers. Hell, an agent—’

Kalinski held up her hand, and pulled her chiming slate from her belt. ‘I’m sorry, sir, we’ll have to talk later. I’ll escort you to the rover, and then to Dome Z where we’ll all go through decon.’

Mardina raised her eyebrows. ‘Decontamination?’

‘Well, yes. This whole dome is a secure environment. It has been since the Hatch was discovered. We’re dealing with an alien artefact here – or at least that’s the best guess we have – with unknown properties. Every time I come out of here, or my twin—’

Beth looked interested. ‘Twin?’

‘Long story. I have to go through decon too. And now you’re here, and who knows what little passengers you’ll have brought back from Proxima c with you? Then, I’m afraid, you’re going to face a barrage of questions, tests, by doctors, physicists . . . Look, we’re making this up as we go along. You may be facing days of processing. I’m sorry.’

Tollemache grinned. ‘The price of fame. God, I’m looking forward to seeing Earth again.’

At least Yuri could tell what he was thinking. Mardina’s look was complicated, calculating; Yuri had no real idea what she had made of this strange turn of events.

And Beth, who had been born under the light of a distant star, who had grown up surrounded by an alien intelligence, who had walked fearlessly into an alien pit on Per Ardua, looked frankly terrified.

CHAPTER 63

Kalinski led them through an airlock directly into a rover, more or less of the kind Yuri was used to from Mars. Once they were all strapped in, Kalinski sat in the left-hand driver’s seat and murmured instructions to an onboard AI.

The rover pulled away from the dome and rolled off. As they did so Yuri glimpsed another rover heading back to the Hatch dome, faces peering through the windows. More scientists on the way in case of more arrivals, perhaps. And Peacekeepers, probably. That would be a characteristic response.

The ride was bumpy, on a road roughly cut through rocky terrain. The windows were very small and looked downward, so you could never see the horizon, let alone the sky with that huge baleful sun. But the light gleamed back painfully from exposed rock faces and the few human artefacts, way marks, signs, small science set-ups.

Kalinski turned to face her passengers. ‘I like to drive myself, generally. But I thought I’d better not take a chance with such a precious cargo.’

‘Thanks,’ Mardina said with a sneer.

‘Oh, come on, Mom,’ Beth said. ‘Colonel Kalinski’s being very kind to us.’ She seemed to be over her partial-gravity nausea, and was looking around more brightly. ‘I can’t see much out of these funny little windows. Is that because of the sun?’

Kalinski said, ‘Yes . . . Do you know much about Mercury, Beth?’

‘Does the sun stay in one place in the sky, like Per Ardua?’

Kalinski took the name on board. ‘Per Ardua. That’s Prox c. OK. No, Mercury has a day that’s two-thirds of its year. It’s to do with tidal resonances. As a result the sun kind of wanders around the sky, as seen from the ground, going west, then east. The whole pattern repeats every two Mercury years. Which is a hundred and seventy-six Earth days.’

Tollemache said, ‘From what I saw the sun is pretty high just here.’

‘That’s right. We’re close to the equator, and it’s local noon – or midsummer. The biggest UN base is at the north pole, on the Boreas Planitia, where there are permanent shadows, ice. This is the Caloris basin. A giant impact crater. Which is why the ground is a broken-up jumble. It’s a difficult place to operate, and we wouldn’t have any kind of permanent base here at all, I guess, if it wasn’t for the kernel beds, and the Hatch being found here. It’s posed all kinds of technical challenges, working here.’

Yuri spotted movement on the desolate ground outside: what looked like tremendous cockroaches, with wide, iridescent wings. They were humans, some kind of astronauts, surface workers, in suits like segmented armour, in brilliant silver. Those wings spread wide from the back. As the rover approached, one of them stood straight and waved. No face was visible behind a golden dome of a helmet. Yuri, bemused, waved back.

Then there were flashes at the windows, brilliant enough to light up the whole interior of the rover. Beth recoiled, rubbing her eyes.

‘Sorry.’ Kalinski pressed a screen, and covers closed over the windows. ‘Camera flashes. I told you there’d been leaks. Your faces will be all over the inner system already. Those guys must be being paid well to risk the discipline charges.’

The rover slowed, and Yuri heard a dull impact on the opaque hull, some kind of docking. Within seconds the hatch opened again, leading to a brightly lit tunnel.

‘Here we go,’ Kalinski said. ‘Dome Z. I’ll be going through decon too, having been in contact with you, and the Hatch. We’ll have to strip, I’m afraid; your clothes will be cleaned and returned later. Men that way, women this, follow me . . .’