The Curator looked surprised. ‘Oh, that’s not for people. Did you imagine booths are just for humans?’ He told them that when Port Sol had first been discovered it had an indigenous fauna, slow-moving inhabitants of the deep cold with liquid helium for blood. ‘Once we farmed them; we transplanted them to other cold worlds. Somehow they survived a million years of cohabitation with mankind - even the dreadful summer we have brought to Port Sol by pushing it into the heart of the system. And now a booth has appeared, right in the middle of their Forest of Ancestors, and, with our help, the Toolmakers, the ones in their motile phase, are passing through to their own destiny. A slow process, I can tell you . . .’ He seemed surprised at their incomprehension. ‘There are many life forms in Sol system - or were, before we came along - but even now many of them survive. And as far as we can tell, every one of them with the remotest level of advancement has been supplied with booths so they can escape the destruction of the sun. Touching, isn’t it? And not only that, there are suggestions in the records that other species, driven to extinction long ago, have been provided with similar escape routes. The Silver Ghosts, for example . . . The booths are evidently part of a long-term rescue strategy, by whoever is responsible. It could be the Xeelee,’ he mused. ‘Some say it is. The Xeelee relish the diversity of life, and seek to protect it, even when it snaps at them, as we have . . .’

The silvered domes at the base of the rocket tower turned out to be the upper levels of much more extensive structures, buried deep under the ice.

The Curator took them down through a hatch in the bottom of the flitter, through a kind of airlock, and then into the interior of the base. They never walked in the vacuum, out on the ice. Symat, who had never walked anywhere you would need a pressure suit, was faintly disappointed to lose out on a little bit of adventure.

The Curator led them along cold, echoing corridors, past closed-off rooms. Just as on Mars there were few people here, it seemed. Symat was getting a sense of Sol system as a series of empty planets and moons, like dusty rooms in a deserted house.

The Curator asked if they wanted to rest or eat, but they were both too excited, or apprehensive. The Curator gave in with a cheerful shrug. ‘Then I’ll take you to the Ascendents.’

He led them along more corridors until they came to a brightly lit area, a complex of corridors that stank strongly of antisepsis, like a hospital. The Curator paused at a door. ‘Now before you go in,’ he told Symat, ‘try not to be afraid.’