This was the trap of history, closing in Symat’s lifetime. For even as one agency was murdering the sun, another, the Xeelee, was driving mankind back from the stars.

‘We were left with nowhere to go,’ Hektor said. ‘Until we discovered the booths.’

Symat said suspiciously, ‘Discovered? ’

‘Yes, discovered. You didn’t imagine they are a human invention?’

Symat supposed he had, but he had never thought hard about it. Besides, it just wasn’t something you talked about.

A few generations back, the booths had simply appeared at scattered locations, studded around the cities and parks of mankind’s remaining worlds. Their operation was simple, the execution awe-inspiring. If you walked through a booth, you would be transported, not just to another place as if this was some fancy teleport system, but to another universe: a pocket universe, as the cosmologists called it, a fold in the fabric of spacetime stitched to the parent by a wormhole-like umbilical. You could walk between universes with your luggage on your back and your child in your arms. And once you were through you would be safe, preserved from Xeelee and photino bird interventions alike.

Nobody was clear exactly how this common knowledge about the booths had reached the human population. Certainly not from the booths themselves, which were one way: nobody came back to tell the tale of what was on the other side. The folk wisdom just seemed to be there, suddenly, in the databases, in the air. But it was believed widely enough for a steadily increasing fraction of humanity to trust their own futures and their children’s to this strange exit.

Hektor said, ‘Obviously there has been speculation. The booths could be an ancient human design, I suppose; who can say what was once possible? Or they could come from some alien culture, though our habit of enslaving, assimilating or eliminating most aliens we came across might seem to argue against that.’ He said conspiratorially, ‘Perhaps it was the Xeelee themselves. What do you think about that? Our greatest foe, eradicating us from the universe - and yet giving us a bolt-hole in the process.’

‘And this is what you want me to walk into,’ Symat said.

Hektor said stiffly, ‘We can’t tell you anything we haven’t told you a dozen, fifty times before. Somehow it never stuck with you, the way it did with other children.’

‘But I thought that if we showed you,’ Pelle said, ‘showed you the world, the sky, the state of things, then it might make things clearer.’

‘Clearer? But walking into a booth is like dying. You can’t come back. And you don’t know what’s on the other side, because nobody ever came back to tell us. Just like dying.’