Alastair Reynolds - Poseidon's Wake

The detonation tore through the ship about a third of the way up the exposed part of the vessel. Above the blast zone, the already leaning edifice started buckling over. Kanu had thought it on the verge of toppling before; now it was fulfilling that promise. Debris, flung in all directions by the detonation, began to rain down around Kanu.

‘Kanu!’ someone shouted.

‘Take the flier!’ someone shouted in return, and it was only when the words were out that he recognised his own voice.

Kanu started running, or what passed for running in the soft, slipping dust under his feet. In the distance, the flier was taking off. The boarding ramp was still lowered, dragging across the ground, and the flier was turning to meet him.

‘No, Garudi,’ Kanu called. ‘It’s too dangerous.’

Kanu glanced back again. A lengthening shadow loomed over him now. The wreck was coming down, bowing to meet him. He could see no sign of Swift, and with an exquisite clarity he knew he stood no chance of reaching the flier.

The seas were heavy, the boat’s rise and fall testing Mposi’s delicate constitution to its limits. For an Akinya, he had always been a poor traveller. Chai and greenbread and paperwork, four square walls and a horizon that stayed still — that was all he really wanted from life.

Even without the tracking device, it was not usually too hard to find Arethusa. They knew her haunts, her favoured latitudes and familiar places. The only large living thing anywhere in Crucible’s waters, she could be tracked using the ancient and venerable methods of submarine warfare. She gave off a mass signature and distorted the waters above her as she swam. Her songlike ruminations, when she talked to herself or recounted Chinese lullabies, sent an acoustic signature across thousands of kilometres. Networks of floating hydrophones triangulated her position to within what was normally a small volume. During times of heavy weather or seismic activity, though, she had stealth on her side.

Nonetheless, the merfolk had narrowed down her location, and swimming out from the hydrofoil they had finally sighted their quarry. But that was as close as the merfolk could get. They owed their very existence to Arethusa — she had been involved since the start of the Panspermian Initiative. Some obscure bad blood lay in their mutual past, however, and she would not deign to talk to them any more.

So Mposi had to swim alone. The merfolk fitted him into a powered swimsuit equipped with a breathing system and launched him into the darkening swell. He gave chase, and of course Arethusa indulged in her usual games, allowing him to come very near before swimming away faster than he could follow. She could keep this up until the cells in his suit ran out of energy.

But Mposi knew that curiosity would eventually prompt her to relent.

‘It’s me,’ he sent into the water ahead of himself, using the suit’s loudspeaker. ‘We need to talk. It’s nothing to do with the tracking device — I’ll never ask such a thing of you again. This is something else, and I need your advice.’

But it always paid to flatter Arethusa.

‘More than your advice,’ Mposi added. ‘Your wisdom. Your perspective on events. No one has your outlook, Arethusa, your breadth of experience or insight.’

It was hard to talk. The suit was powered, but it still required some effort to drive and coordinate his movements. His lungs burned, even when he turned up the oxygen flow in his mask. She would hear his weakness, he felt sure. She would hear it and mock him for it.

‘Something’s happened,’ Mposi carried on after he had swum a dozen more strokes. ‘A signal’s come in from a long way off. We don’t understand why it’s been sent to us, or what we should make of it. There’s a chance it has something to do with—’

‘That dolphin-torn, that gong-tormented sea.’

She had answered, in her fashion, and his suit had picked up the emanations and converted them into natural Swahili. Arethusa did in fact speak Swahili, or at least she had been able to in the past. Lin Wei, the girl she had once been, had attended school in East Equatorial Africa.

Dolphin-torn, gong-tormented.

He was doing the one thing he had meant not to do — getting on her nerves.

But she slowed, allowing him to narrow the distance between them, and he was soon approaching her great fluked tail. His mask showed her body, two hundred metres away, as a whiskered oval. She had been two hundred metres long when she hurt him; now she had grown by a third as much again. Arethusa was the oldest sentient organism, as far as Mposi knew. But the cost of that sentience was an endless need to grow. To grow, and to move further and further from the epicentre of human affairs. The murmurings the hydrophone network picked up were increasingly strange, increasingly suggestive of a mind that had slipped its moorings.

And yet he would still risk all for an audience.

‘The signal,’ Mposi persisted, ‘was aimed at us, unidirectional. Low power, even allowing for the transmission distance — and while it repeated long enough for us to recover the content, it was only active for a short while. Doesn’t that interest you, Arethusa? I’ll tell you something else. The message mentioned Ndege. That’s a name you recognise. My sister, of course. Another Akinya. And while you might not be blood, our business is always your business.’

Arethusa had stopped in the water, so Mposi slowed his rate of approach, painfully conscious of what those flippers could do to him. Like a great spacecraft making a course adjustment, the whale turned gradually until Mposi was hovering just before her left eye. Scarcely any light now reached them, so Mposi was reliant on his goggles’ sonar overlay. He shivered, as he had shivered before, at the magnitude of her — and the very human scrutiny of her eye, looking at him from a cliff of grooved flesh.

‘I thought I killed you once, Mposi.’

‘You gave it a good try. The fault was mine, though. I understand there was nothing personal in it.’

‘Do you?’

As large as she was, she could move with surprising speed. He had allowed himself to enter her sphere of risk.

‘Gliese 163,’ he said. ‘That’s the name of the star in the other solar system. We know a little bit about it: Ocular data, a few later observations.’

‘No one has mentioned Ocular in a very long time.’

That was true, but Mposi had not made the reference thoughtlessly. The vast telescope had been Lin Wei’s brainchild, and she had seen it hobbled by Akinya interference. There was danger in bringing that up, he realised. But he was also seeking a direct connection to her past.

‘Eunice was your friend, before it all turned bad over Ocular. That’s true, isn’t it?’

‘You never knew her. What right have you to speak of her?’

‘None, except that I’m her great-great-great-grandson. And I think she may have some connection with the message.’

Arethusa’s flukes stirred, moving tonnes of water with each stroke. ‘You think ?’

‘There hasn’t been time for any human ship to get that far out, and send a return transmission. But the Watchkeepers? We don’t know how they move or how fast they can travel. What we do know is that they took three of us with them — the Holy Trinity. Chiku Green, of course. Dakota. And the Eunice construct.’

‘The map is not the territory.’

‘I understand that the construct isn’t the same thing as your flesh-and-blood friend. But she was getting closer, becoming… what’s the word? When a curve meets a line? Asymptotic?’

‘Your point, Mposi?’

‘Someone has to go out there. We can’t just pretend this message never arrived. Someone went to the trouble to send it. The least we can do is respond.’