One feature, popular but hotly debated ethically, was the ability to stop the growth of your child at a certain age. You could stretch out a childhood for as long as you wanted, enough to match your own long lifespan. Some people kept their Virtual children as perpetual infants; generally, however, eight to ten years old was the chosen plateau range.

‘I’m twelve,’ Mela said. ‘Few ever got as old as me. For a long time I’ve been surrounded by kids younger than me.’

‘A long time? How long?’

Mela considered. ‘Oh, two hundred years, nearly.’

Symat, shocked, didn’t know what to say.

Times changed, Mela said. Now, in increasing numbers, people were leaving the world behind altogether, passing through the transfer booths to an unknown destination beyond. And the Virtual children couldn’t follow: you could take your pots and pans, but you couldn’t take your Virtual child.

More than that, Mela told him mildly, Virtual children had simply gone out of fashion, as had so many technological toys before them. It became embarrassing to admit you needed such an emotional crutch.

For all these reasons, the children were shut down - or more commonly just abandoned, perhaps after centuries of companionship every bit as intense as the bond between a parent and a real child.

‘Every last mother said she would come back. I always knew the truth. I was twelve years old. But Chem is only eight. He’ll be eight for ever. And he still believes. Every day he is disappointed.’

Every day for centuries, Symat thought, Chem wakes up full of pointless hope, trapped in childhood. ‘Tod seems to understand.’

‘He’s actually younger than Chem, but he’s tougher minded.’

‘How come?’

She shrugged. ‘His parents had him designed that way. You could choose what you liked. Chem’s parents must have wanted a child more dependent, more vulnerable.’

‘But they abandoned him anyway.’

‘Oh, yes.’

Symat said, ‘But I still don’t see—’

He heard a piercing scream. Mela broke off and ran into the township. Symat hurried after her.

They came to an open plaza. A number of children had gathered, perhaps a dozen, none older than eight or nine. No, not children - they were more Virtuals, as Symat could tell from the sparkling pixels and tiny pings that marked petty protocol violations. They all wore bland shifts and coveralls like Mela and the boys.

And these kids stood in a loose ring around Chem and Tod. The boys crouched on the floor, clinging to each other.

Mela ran forward. ‘Get away from them!’

Symat hurried after her. ‘What kind of game is this?’

‘No game,’ she called back. ‘They are bloodsuckers. They are trying to kill the boys.’

‘Kill them? How do you kill a Virtual?’