They bundled back into the rover, and the ColU followed. They’d only travelled a short way when, picked out in the vehicles’ lights, they all saw something ahead, on the ice, picked out by Liu’s ageing but still sharp eyes.

A flag, hanging limp on a pole. UN blue.

They pulled the vehicles up short, suited up, and climbed out onto the ice once more. The air was bitterly cold, and their breath misted around their heads. The three of them stood side by side, illuminated by the lights of the rover and the ColU.

And before them, clearly visible in the glow of the lights, was the flag, and what looked like a tent, slumped. Beyond the tent the ice surface fell away, perhaps into some kind of crater. None of them had an idea what any of this meant.

They walked forward, over hard, rough ice. The ColU followed, its lights dipped. The flag was fixed to a kind of improvised ski pole, stuck in the ice. They walked past it, staring.

At the tent, Yuri lifted a flap, stiff with ice. In the light of his hand torch he saw a body, inside the tent. He stepped back.

Wordlessly, Liu went inside to inspect the body.

Yuri and Stef walked around the rest of the site. Aside from the tent, there was a heap of scattered equipment on a frozen groundsheet, a pair of homemade-looking skis, a kind of improvised ice-bike, a heap of stores – and a gadget about a metre tall with an inlet hopper, an outlet compartment that looked like a miniature intensive-care chamber, and finely inscribed instructions on the casing.

‘What’s this?’ Yuri asked. ‘Some kind of iron cow?’

‘Not that,’ said the ColU.

Liu called them over.

Reluctantly they returned to the tent, where Liu stood over the body. It was a man. He lay wearing only an antique military uniform, no protective clothing. There was no sign of decay. But then, Yuri realised, he must have frozen solid before the bacteria in his body could have begun to consume him – and on Per Ardua, there was nothing yet that could consume a human corpse. The very processes of death were alien, on this alien world.

The dead man bore a UN roundel on his sleeve. A sheen of ice lay over his features. He was smart, clean-shaven, even his hair combed. He looked like an astronaut.

Stef said, ‘I guess he wanted to die in his uniform, huh.’

Liu looked at her. ‘You know who this is?’

‘I know who it has to be.’

‘Dexter Cole?’ Yuri asked. The pioneer who had come to Proxima on some wild solo mission, half-baked even compared to the Ad Astra venture, in the decades Yuri had slept away in cryo.

‘Yes. There is identification here.’

They all backed out of the tent.

Yuri said, ‘The colonists used to think Cole’s ghost was roaming around Per Ardua. Remember that, Liu?’

‘I guess we might have been right about that.’

‘So what happened to him?’

Liu pointed to a heap of paper he’d gathered together on the ice. ‘He left a journal. A video diary too. But there’s also a letter, one page.’ He held this up in his gloved hand. ‘The bullet-point summary. Evidently he wanted to be sure we got the message. He did what he had to do. He says that, over and over. I guess he didn’t want to be remembered a failure. Or worse.’

Stef said, ‘He did what he had to do? What does that mean? He evidently made it to the Prox system. He was the first human to cross interstellar space, the first to land on Per Ardua. He’ll be remembered for that.’

‘Yes,’ said Liu. ‘But he was actually here to colonise, remember. It went wrong – according to the note. He crashed, somewhere on this dark side, the frozen side. He had no comsat, he couldn’t even send a message home to say what had happened. Much of his equipment was wrecked. He seems to have improvised all this gear. A kind of ski-bike, to get around on the ice. He hauled everything else after him.’

‘He came here, to the antistellar,’ Stef said. ‘Why?’

‘He wanted to be found, or his body anyhow. He knew he couldn’t make it to the near side. Where else are people going to come, on the dark side? We zoomed straight here. He wanted people to know his story. And he didn’t want to be thought of as a monster.’

Yuri frowned. ‘Why the hell would anyone think that?’

Liu kicked the processing gadget. ‘This isn’t an iron cow, not a food machine. Dexter Cole was supposed to be the father of a whole colony. That was the idea. The strategy was that he would bring human embryos, frozen in here, that he’d thaw out one by one, and feed up, and raise. Twenty little colonists in the light of Proxima, with Cole as the godfather. That was the vision.’

‘Instead of which . . .’

‘Instead of which he was lost in the dark, and starving. He grew the embryos, all right. He must have found nutrients somewhere to feed the incubator – volcanic pools, I guess. But what he did with them . . .’

‘Oh, God.’ Stef knelt on the groundsheet, by the machine. She picked up something from the floor – a heap of white fragments, like a tiny builders’ midden, Yuri thought. Bones. Finger bones, perhaps. Stef put them respectfully back where she’d found them.

Yuri looked down at the dead man’s stern, placid features, and wondered how sane he had been, in the end, alone in the icy dark with his only food source, this grisly repast.

Liu shrugged. ‘What would you have done? What would any of us do? The kids couldn’t have survived here anyhow.’

The ColU said evenly, ‘That’s not all he did here, though. I have inspected the wider area. Dexter Cole did more than just survive. There’s something else here. In the ice, I mean. Something he found.’

They looked at each other. Then they hurried over to the ColU, which was standing at the lip of the depression in the ice.

It wasn’t a natural formation, nothing like a crater. It was a pit. Cole had blown a pit in the ice. And at the bottom, it looked like he had got to work with a pick of some kind. He had exposed a sheet of a grey metal-like substance, and a fine circular seam, a few metres across.

‘Dexter Cole evidently became curious,’ the ColU said. ‘About this place, the antistellar, a point of obvious significance. Perhaps he retained some equipment from his crashed ship. He may have detected structures beneath the ice, with radar or sonar echoes. And he certainly had explosives.’

They all scrambled down into the shallow depression. The ColU rolled forward, playing its lights over them.

‘A Hatch,’ Yuri said. ‘He only found another fucking Hatch, ColU!’

‘Yes. And diametrically opposite the first, at the substellar Hub. Also there is a field of kernels, buried in the rock of this area.’

‘What is going on with these Hatches?’

Stef knelt and pointed, grinning. ‘Look. Hand-shaped lock grooves. We can open this.’

Liu stared. Then he held up Cole’s one-sheet missive, scanning it quickly. ‘Cole says this was featureless when he found it. He even made a sketch. Look. He took images on his slate, he says. No hand marks.’

‘Then it changed,’ Yuri said. ‘Just as the day side Hatch changed when we first went into it.’

‘And the one on Mercury, the same,’ Stef said.

Yuri looked at her. ‘What are we going to do about it?’

She grinned. ‘What do you think?’

Liu backed away, hands raised. ‘Whoa. You’re talking about going into that thing? Count me out.’

The ColU said, ‘I think it is my duty to point out that you are entirely unprepared, Yuri Eden.’

‘That never stopped us before.’

‘True. But there may not even be breathable air on the other side. Consider Mercury—’

‘We’re going anyhow.’ He grinned at Stef, who grinned back. ‘We’re done with Per Ardua, aren’t we? Done with Earth. Especially if they import their war here.’

The ColU stood still, its floods splashing light over the Hatch in its pit. ‘You are determined.’

‘That’s right.’

‘In that case I have a request.’