And then he returned to continue the discussion.

Chao-Li Wu was leaning back in his seat now, his astute face showing no signs of weariness.

‘Let me summarize,’ he said. ‘In the absence of superluminal flight, this Neighbor Star - I shall call it Nemesis, as you do - is the nearest star to the Solar System, so that any ship making its way to the stars would be bound to stop here first. Once all humanity has true superluminal flight, however, distance is no longer a factor and human beings will not search out the nearest star, but the most comfortable star. The search will be on for Sun-like stars that happen to be circled by at least one Earth-like planet. Nemesis will be put to one side.

‘Rotor, which has, till now, apparently made a fetish of secrecy, to keep others away and to reserve this stellar system for itself, need do so no more. Not only will this system be unwanted by other Settlements, but Rotor itself may no longer want it. It may choose, if it so desires, to search out Sun-like stars for itself. There are billions of such stars in the spiral arms of the Galaxy.

‘In order for Rotor to have superluminal flight, it might occur to you that you could point a weapon at me and demand all I know. I am a mathematician, a highly theoretical one, and my information is limited. Even if you were to capture our ship itself, you would learn very little from it. What you must do is to send a deputation of scientists and engineers to Earth, where we could train you adequately.

‘In return, we ask for this world, which you call Erythro. It is my understanding that you do not occupy it in any way except for the presence of this Dome, which is used for astronomical and other kinds of research. You are living in Settlements.

‘Whereas the Settlements of the Solar System can wander off in search of Sun-like planets, the people of Earth cannot. There are eight billion of us who must be evacuated in a few thousand years and, as Nemesis approaches more and more closely to the Solar System, Erythro will more and more easily serve as a way station on which to place Earthpeople until such time as we can find Earth-like worlds to transfer them to.

‘We will return to Earth with a Rotorian of your choosing as proof that we were really here. More ships will be built and they will return - you can be sure we will return, for we must have Erythro. We will then take back your scientists, who will learn the technique of superluminal flight, a technique we will also grant to the other Settlements. Does all this adequately summarize what we have decided?’

Leverett said, ‘It's not all quite that easy. Erythro will have to be terraformed if it is to support any sizable number of Earthpeople.’

‘Yes, I have left out details,’ said Wu. ‘These will have to be dealt with, too, but not by us.’

‘True, Commissioner Pitt and the Council will have to decide on Rotor's behalf.’

‘And the Global Congress on Earth's behalf, but with so much at stake, I don't foresee failure.’

‘There will have to be safeguards. How far can we trust Earth?’

‘About as far as Earth can trust Rotor, I imagine. It may take a year to work out safeguards. Or five years. Or ten years. It will take years, in any case, to build an adequate supply of ships with which to begin, but we have a program that should last several thousand years, one that will end with the necessary abandonment of Earth and the beginning of the colonization of the Galaxy.’

‘Assuming there are no competing intelligences to be taken into account,’ growled Leverett.

‘An assumption we can make until we are forced to abandon it. That is for the future. Will you consult your Commissioner now? Will you choose your Rotorian to accompany us and allow us to leave for Earth as soon as possible?’

Now Fisher leaned forward. ‘May I suggest that my daughter, Marlene, be the one-’

But Genarr did not allow the sentence to be completed. ‘I'm sorry, Crile. I've consulted her. She will not leave this world.’

‘If her mother goes with her, then-’

‘No, Crile. Her mother has nothing to do with it. Even if you wanted Eugenia back, and Eugenia were to decide to go with you, Marlene would still remain on Erythro. And if you decided to stay here to be with her, that would do you no good either. She is lost to you, and to her mother as well.’

Fisher said angrily, ‘She's only a child. She can't make these decisions.’

‘Unfortunately for you, and for Eugenia, and for all of us here, and perhaps for all of humanity, she can make these decisions. In fact, I have promised that when we are through here, as I think we now are, that we will acquaint her with our decisions.’

Wu said, ‘Surely that is not necessary.’

Leverett said, ‘Come, Siever, we don't have to go to a little girl for permission.’

Genarr said, ‘Please listen to me. It is necessary, and we do have to go to her. Allow me to try an experiment. I am suggesting that Marlene be brought in here so that we can tell her what we have decided. If one of you thinks that is not desirable, let him leave. Let him stand up and leave.’

Leverett said, ‘I think you've taken leave of your senses, Siever. I have no intention of playing games with a teenager. I'm going to speak to Pitt. Where do you keep your transmitter?’

He stood up and, almost at once, staggered and fell.

Wu half-rose in alarm, ‘Mr Leverett-’

Leverett rolled over and held up his arm. ‘Help me up, somebody.’

Genarr helped him to his feet and back into the chair. ‘What happened?’ he asked.

‘I'm not sure,’ said Leverett. ‘I had this blinding headache for just a moment.’

‘So you were not able to leave the room.’ Genarr turned to Wu. ‘Since you don't think seeing Marlene is necessary, would you care to leave the room?’

Very carefully, eyes fixed on Genarr, Wu rose slowly from his chair, winced, and sat down again.

He said politely, ‘Perhaps we had better see the young woman.’

Genarr said, ‘We must. On this world, at least, what that young woman wishes is the law.’

‘No !’ said Marlene so forcibly that it amounted almost to a shriek. ‘You can't do it!’

‘Can't do what?’ said Leverett, his white eyebrows drawing close to the furrowed line between.

‘Use Erythro for a way station - or for anything.’

Leverett stared at her angrily, and his lips drew back as if to speak, but Wu intervened. ‘Why not, young woman? It is an empty, unused world.’

‘It is not empty. It is not unused. Uncle Siever, tell them.’

Genarr said, ‘What Marlene wants to say is that Erythro is occupied by innumerable prokaryote cells capable of photosynthesis. That is why there is oxygen in Erythro's atmosphere.’

‘Very well,’ said Wu. ‘What difference does that make?’

Genarr cleared his throat. ‘Individually, the cells are as primitive as life can be above the virus level, but, apparently, they cannot be treated individually. Taken all together, they form an organism of enormous complexity. It is world-girdling.’

‘An organism?’ Wu remained polite.

‘A single organism, and Marlene calls it by the name of the planet, since they are so intimately related.’

Wu said, ‘Are you serious? How do you know about this organism?’

‘Chiefly through Marlene.’

‘Through the young woman,’ said Wu, ‘who may be - a hysteric?’

Genarr lifted a finger. ‘Do not say anything seriously against her. I'm not sure that Erythro - the organism - has a sense of humor. We know chiefly through Marlene - not entirely. When Saltade Leverett stood up to leave, he was knocked down. When you half-rose a while ago, perhaps also to leave, you were clearly uncomfortable. Those are the reactions of Erythro. It protects Marlene by acting directly on our minds. In the early days of our existence on this world, it inadvertently caused a small epidemic of mental disease that we called the Erythro Plague. I'm afraid that, if it wishes, it can produce irrecoverable mental damage; and, if it wishes, it can kill. Please do not test this.’

Fisher said, ‘You mean it is not Marlene who-’

‘No, Crile. Marlene has certain abilities, but they don't extend to the point of doing harm. It is Erythro that is dangerous.’

‘How do we stop it from being dangerous?’ asked Fisher.

‘By listening politely to Marlene, to begin with. Then, too, let me be the one to talk with her. Erythro, at least, knows me. And believe me when I say that I want to save Earth. I have no desire to bring about the death of billions.’

He turned to Marlene. ‘You understand, Marlene, don't you, that Earth is in danger? Your mother showed you that the close approach of Nemesis might destroy Earth.’

‘I know that, Uncle Siever,’ said Marlene in an agonized voice, ‘but Erythro belongs to itself.’

‘It might want to share, Marlene. It allows the Dome to remain here on the planet. We don't seem to disturb it.’

‘But there are less than a thousand people in the Dome and they stay in the Dome. Erythro doesn't mind the Dome because that means it can study human minds.’

‘It can study human minds all the more when Earth-men come here.’

‘Eight billion of them?’

‘No, not all eight billion. They'll come here to settle down temporarily and then go off somewhere. At any one time, there'll only be a fraction of the population here.’

‘It will be millions. I'm sure it will be. You can't squeeze them all into a dome and supply them with food and water and all they'll need. You'll have to spread them out on Erythro and terraform it. Erythro couldn't survive it. It would have to protect itself.’

‘Are you sure of that?’

‘It would have to. Wouldn't you?’

‘It would mean the death of billions.’

‘I can't help that.’ She pressed her lips together, then said, ‘There's a different way.’

Leverett said gruffly, ‘What's the girl talking about? What different way?’

Marlene glanced briefly in Leverett's direction, then turned to Genarr. ‘I don't know. Erythro knows. At least - at least it says that the knowledge is here, but it can't explain.’

Genarr held up both arms to stop what might have been a flurry of questions. ‘Let me talk.’

Then he said very quietly, ‘Marlene, be calm. If you're worried about Erythro, that is useless. You know it can protect itself against anything. Tell me what you mean when you say Erythro can't explain.’