Symat could see she was torn. ‘I’ll come back,’ she said. ‘This could be important. Just stay out of the way of the bloodsuckers and you’ll be fine.’

Symat’s mother put her own Virtual arm around Mela. ‘Come, dear.’ They started walking across the sand towards the flitter.

Chem, desperate, called after Symat, ‘You promised you’d stay, you promised you’d keep us alive.’

‘I’ll come back.’

‘They always say that. You won’t. You won’t! . . .’

Symat followed Mela and his mother, his heart breaking.

II

The flitter arrowed with perfect accuracy towards Kahra, capital city of Mars, where Symat had grown up. The ease of the journey was galling, after Symat’s slog on foot through the echoing deserts.

And as the flitter dipped low over the rooftops of Kahra, he saw lines of people snaking towards the transfer booths. The human population of Mars was passively draining into another universe. Symat glanced at his father, wondering if this part of the flight had been set up deliberately to show him the booths and the patient lines, to make a point. Hektor returned his gaze, impassive.

Symat’s parents’ villa, on the outskirts of Kahra, was spacious, airy. Mela and Symat wandered through it. The glass walls shone like fire in the light of the sun. Even after a million years on Mars some deep instinct made you aware that this tall, open design would have been impossible on heavy Earth, and the place felt all the more remarkable.

‘It’s beautiful,’ Mela said.

After his abortive adventure Symat wanted to puncture her awe. ‘It isn’t so special. There are much grander buildings than this, all over Kahra, in fact all around the twilight belt. All empty,’ he said harshly. ‘You can just walk in and take whatever you want.’

‘But this is home, to you. That’s the most important thing about it.’

‘I don’t like being here.’

‘But you don’t have anywhere else to go. You’re all stuck here together, you and your family.’

He studied her. ‘You’re very smart about this stuff. Perceptive.’

‘You think I’m too smart.’ Just briefly her projected image seemed to waver.

Symal felt angry. Why did he have to make friends with a weird, superhuman two-hundred-year-old Virtual? Couldn’t he just have found somebody normal? ‘You’re not even here, are you? Not really. You’re just a projection of some vast cobwebby thing.’

‘I’m here.’ She tapped her head. ‘It’s just that I hear things. I can’t help it. I’ll go away, if you like.’

‘No.’ It had been a long time since anybody else of Symat’s age had come here. There had been few children around to begin with, and all his childhood companions had long since followed their parents into the booths. He couldn’t bear the thought of being left alone again. ‘You’ll have to do,’ he said.