Looking down now, it struck Symat for the first time that Kahra was set slap in the middle of the twilight band, exactly poised between dark and light. But he knew that when Kahra had been founded Mars had still spun on its axis. He wondered if that positioning was a happy accident - or if the slowing rotation of Mars had somehow been managed so that Kahra ended up exactly where it needed to be. He had no idea how you might control the spin of a whole world, but then, it was said, the people of the past had had powers beyond the imagination of anybody now alive.

As the flitter swept through its rapid suborbital hop, the sun rose. Bloated, surrounded by a churning corona, the sun’s scarlet face was pocked by immense spots. Symat’s father had told him that the whole of the sun was a battleground between forces beyond human control, and from here it looked like it.

The flitter swooped down towards Dayside, the sunlit face of Mars. On blasted crimson rock cities still glittered. But there was no sign of life, no movement in the cities, and the canals were bone dry.

Hektor said, ‘Look down there. Nothing left but bugs in the deep rocks. Everything that can burn in those cities has gone already. Son, if you transplanted our villa down there it would turn into a shining puddle of melted glass. And it’s getting worse.’

‘Because the sun is still heating up.’

‘So it is. There is nothing we can do to reverse this. Soon the twilight belt will close, squeezed between hot and cold, and Mars will be uninhabitable, just as it was before humans came and terraformed it. And the last of us will have to leave, or die.’

This desolate prospect filled Symat with gloom, which it was in his nature to resist. ‘It might not come to that. What if the sun cools again?’

Pelle touched Symat’s arm. ‘It won’t. Those who are destroying the sun won’t allow it.’

To swell into a giant would have been the sun’s eventual fate, but not for billions of years yet. This premature destabilisation of the sun was deliberate. Creatures, malevolent and relentless, swarmed in its core, puddling the fusion processes there, and so compressing aeons of a stellar lifetime into mere megayears. And Sol was not the only star being smothered in its own heat. You only had to look around the sky, littered with red stars, to see that. ‘But it’s not personal,’ a teacher had told Symat once, with black humour. ‘The photino birds in the heart of the sun probably don’t even know we humans exist . . .’

‘The sun is dying,’ Hektor said with bleak finality, ‘and Mars is dying with it, and there isn’t a thing we can do about it. And then there’s the Scourge.’