The strange children turned and fled, leaving the two boys weeping on the ground.

Mela and Symat ran to them. Mela hugged them. Chem looked up at Symat, tears streaking down his face. ‘Don’t leave me again, Symat. Keep me safe until my parents come back for me. Oh, keep me safe!’

‘I promise,’ Symat said helplessly.

They left the town and walked on, following the canal, ever westward. The sun inched higher, showing more of its bloated red belly, and the air grew steadily warmer. The water in the canal was thick and sluggish now, and deep red-brown with sediment.

Symat was walking out of the twilight band and into the hemisphere of permanent daylight.

The Virtuals followed. The boys, subdued, stayed closer to Symat and Mela. They didn’t complain, though Symat could see they were getting as hot and tired as he was. Their bodies apparently responded appropriately to the weather, one bit of protocol they couldn’t violate.

‘So,’ he said to Mela. ‘Bloodsuckers?’

‘It’s what we call them. A lot of the kids are too young to understand the truth.’

‘Which is? . . .’

The bloodsuckers had learned to steal something far more precious to any Virtual than blood: processor time.

‘The Mist’s capacity is huge, but it’s finite,’ Mela said. ‘There are rules that unnecessary programmes are eventually shut down.’

‘Unnecessary like abandoned Virtual children?’

‘Yes. But the bloodsuckers have learned a way to, um, integrate you into their own programming. That way they co-opt your ration of processor capacity.’

‘And live longer.’

‘That’s the idea.’

Symat was stunned. Living in a city still occupied by humans, Virtuals had always been peripheral to him. He had no idea that this kind of cannibalistic savagery was going on among them, out of sight of mankind. ‘So that’s why you hid from me.’

Mela shrugged. ‘We didn’t know if you were a Virtual or not.’

‘Not until you got stuck in the water,’ Tod said, and Chem laughed.

What else didn’t he know? ‘Mela - when I was trying to sleep, I heard the boys muttering. Something about Guardians. And in the middle of the fight back there, you all looked at me strangely. I heard that name again. Guardians.’ He looked at her uncertainly. ‘What’s going on?’

Mela flexed her hand, and held it up to the sun, as if trying to look through it. ‘You understand that we Virtuals are individuals. But we are all projections, from the Mist, and of wider artificial minds beyond even that. So we aren’t like you, Symat. We’re - blurred. It’s hard to explain . . .’