When she opened her eyes again, the stars framed a Spline ship, rolling overhead, and the concerned face of her cadre leader, Bryn.

The Spline rose high, and the site of Minda’s crash dwindled to a pinpoint, a detail lost between the tracery of the abandoned city and the volcano’s huge bulk.

‘It was the motion of the vegetation that our sensors spotted,’ Bryn said. Her face was sombre, her voice tired after the long search. ‘That was what drew us to you. Not your heat, or even your ghost’s. That was masked by the volcano.’

‘Perhaps the ghost meant that to happen,’ Minda said.

‘Perhaps.’ Bryn glanced at the ghost’s hide, spread on a wall. ‘Your ghost was astonishing. But its morphology is a logical outcome of an evolutionary drive. As the sky turned cold, living things learned to cooperate, in ever greater assemblages, sharing heat and resources. The thing you called a silver ghost was really a community of symbiotic creatures: an autarky, a miniature biosphere in its own right, all but independent of the universe outside. Even the skin that saved you was independently alive . . . This is a new species for us. Evidently we have reached a point where two growing spheres of colonisation, human and ghost, have met. Our future encounters will be interesting.’

As the planet folded on itself, Minda saw the colony of the ghosts rising over the chill horizon. It was a forest of globes and half-globes anchored by cables; gleaming necklaces swooped between the globes. The colony, a sculpture of silver droplets glistening on a black velvet landscape, was quite remarkably beautiful.

But now a dazzling point of light rose above the horizon, banishing the stars. It was a new sun for Snowball made by humans, the first of many fusion satellites hastily prepared and launched. The ghost city cast dazzling reflections, and the silver globes seemed to shrivel back.

Bryn said, watching her, ‘Do you understand what has happened here? If the ghosts’ evolution was not competitive as ours was, they must be weaker than us.’

‘But the ghost gave me its skin. It gave its life to save me.’

Bryn said sternly, ‘It is dead. You are alive. Therefore you are the stronger.’

‘Yes,’ Minda whispered. ‘I am the stronger.’

Bryn eyed her with suspicion.

Where the artificial sun passed, the air melted, pooling and vaporising in great gushes.

After that first contact, two powerful interstellar cultures cautiously engaged. One man, called Jack Raoul, played a key role in developing a constructive relationship.

To understand the creatures humans came to know as ‘Silver Ghosts’ - so Raoul used to lecture those who were sceptical about the mission that consumed his life - you had to understand where they came from.