How early had she known? From the moment she had named the star Nemesis? Had she felt what it was and what it meant, and had she named it appropriately without conscious thought?

When she had first spotted the star, it had been only the act of finding it that counted. There had been no room in her mind for anything but immortality. It was her own star, Insigna's Star. She had been tempted to call it that. How glorious that had sounded, even as she had reluctantly avoided it with a hollow internal grimace of mock modesty. How unbearable it would have been now if she had fallen into that trap.

After the discovery, there had come the shock of Pitt's demand for secrecy, and then the furious preparation for the Leaving. (Would that be what it would be called in the history books someday? The Leaving? Capitalized?)

Then, after the Leaving, there were two years in which the ship skipped steadily and barely into and out of hyperspace - and the endless calculations that were involved in that hyper-assistance, for which astronomical data was constantly required, with herself supervising the supply. The density and composition of interstellar matter alone-

At no time in those four years had she been able to think of Nemesis in detail; not once could she zero in on the obvious.

Was that possible? Or did she simply turn away from what she did not want to see? Had she deliberately sought refuge in all the secrecy and scurry and excitement that presented itself to her?

But there came a time when the last hyperspatial period was behind them; when, for a month, they would be decelerating through an initial hail of hydrogen atoms, which they struck with such speed that those atoms were converted into cosmic ray particles.

No ordinary space vehicle could have endured that, but Rotor had a thick layer of soil around it that had been thickened for the trip, and the particles were absorbed.

There would come a time, she had been assured by one of the hyperspatialists when one would enter and leave hyperspace at ordinary speeds. ‘Given hyperspace in the first place,’ he had said, ‘no new conceptual breakthrough is required. It's just engineering.’

Maybe! The remaining hyperspatialists, however, considered the notion so much star exhaust.

Insigna hurried in to see Pitt when the appalling truth descended upon her. He had had little time for her in the last year, and she had understood. There was a certain tension that became more and more evident as the excitement of the trip wound down, as people realized that in a matter of months they would be in the neighborhood of another star. They would then have the constant problem of having to survive over a long period in the vicinity of a strange red dwarf star without any guarantee of reasonable planetary material to serve as a supply source, let alone a living place.

Janus Pitt no longer looked like a young man, although his hair was still dark, his face unlined. Only four years had passed since she had come to him with the news of Nemesis' existence. There was, however, a harried look in his eyes, a sense of having had his joy rubbed away and his cares left naked to the world.

He was Commissioner-elect now. Perhaps that might account for a great deal of what might be troubling him, but who could tell? Insigna had never known true power - or the responsibility that accompanied it - but something told her it might have the capacity for souring one who did.

Pitt smiled at her absently. They had been forced to be close when they had shared a secret that at first no-one - and then almost no-one - had shared with them. They could then talk unguardedly with each other, when they could not do so with anyone else. After the Leaving, however, when the secret was revealed, they had grown apart again.

‘Janus,’ she said, ‘there is something eating away at me and I had to come to you with it. It's Nemesis.’

‘Is there anything new? You can't say you've found out it isn't where you thought it was. It's right out there, less than sixteen billion kilometers away. We can see it.’

‘Yes, I know. But when I first found it, at a distance of two-plus light-years, I took it for granted that it was a companion star, that Nemesis and the Sun were circling a common center of gravity. Something that close would almost have to be. It would be so dramatic.’

‘All right. Why shouldn't things be dramatic now and then?’

‘Because as close as it is, it is clearly too far away to be a companion star. The gravitational attraction between Nemesis and the Sun is terribly weak, so weak that the gravitational perturbations of nearby stars would make the orbit unstable.’

‘But Nemesis is there.’

‘Yes, and more or less between ourselves and Alpha Centauri.’

‘What has Alpha Centauri got to do with it?’

‘The fact is that Nemesis is not much farther from Alpha Centauri than it is from the Sun. It's just as likely to be a companion star of Alpha Centauri. Or, more likely, whichever system it belongs to, the presence of the other star is now disrupting it, or has already disrupted it.’

Pitt looked at Insigna thoughtfully and tapped his fingers lightly on the arm of his chair. ‘How long does it take Nemesis to go around the Sun - assuming it's the Sun's companion?’

‘I don't know. I'd have to work out its orbit. That's something I should have done before the Leaving, but there were so many other things occupying me then, and now, too - but that's no excuse.’

‘Well, make a guess.’

Insigna said, ‘If it's a circular orbit, it would take Nemesis just over fifty million years to make a circuit about the Sun, or, more properly, about the center of gravity of the system, with the Sun making a similar circuit. The line between the two, as they moved, would always pass through that center. On the other hand, if Nemesis is following a highly elliptical orbit and is now at its farthest - as it must be, for if it ventured farther still, it would certainly not be a companion star - then perhaps as little as twenty-five million years.’

‘Last time, then, that Nemesis was in this position, more or less between Alpha Centauri and the Sun, Alpha Centauri must have been in a much different position than it is now. Twenty-five to fifty million years would move Alpha Centauri, wouldn't it? How much?’

‘A good fraction of a light-year.’

‘Would that mean that this is the first time Nemesis is being fought over by the two stars? Till now, would it have been circling peacefully?’

‘Not a chance, Janus. Even if you count out Alpha Centauri, there are other stars. One star may have arrived now, but there had to be another star in interfering distance at some other part of its orbit in the past. The orbit just isn't stable.’

‘What's it doing here in our neighborhood, then, if it isn't orbiting the Sun?’

‘Exactly,’ said Insigna.

‘What do you mean, “exactly”?’

‘If it were orbiting the Sun, it would be moving at a speed, relative to the Sun, of somewhere between eighty and one hundred meters a second, depending on Nemesis' mass. That's very slow motion for a star, so it would seem to stay in the same place for a long time. It would therefore remain behind the cloud for a long time, especially if the cloud is moving in the same direction relative to the Sun. With such a slow motion and its light dimmed, it's no wonder it's never been noticed till now. However-’ She paused.

Pitt, who made no effort to seem devouringly interested, sighed and said, ‘Well? Can you get to the point?’

‘Well, if it's not in orbit about the Sun, then it is in independent motion and it should be moving relative to the Sun at a hundred kilometers a second or so, a thousand times as fast as if it were in orbit. It just happens to be in our neighborhood now, but it is moving on, will pass the Sun, and will never return. But, just the same, it stays behind the cloud, scarcely budging from its position.’

‘Why should that be?’

‘There's one way it can be moving at a good clip, and yet not seem to be moving from its position in the sky.’

‘Don't tell me it's vibrating back and forth.’

Insigna's lip curled. ‘Please don't try to make jokes, Janus. This isn't funny. Nemesis might be moving more or less straight toward the Sun. It wouldn't be shifting either to the right or left, so that it would not seem to be changing position, but it would be coming right toward us; that is, right toward the Solar System.’

Pitt stared at her in surprise. ‘Is there evidence for that?’

‘Not yet. There was no reason to take the spectrum of Nemesis when it was first spotted. It was only after I had noticed the parallax that a spectral analysis would have made sense, and then I never got around to it. If you remember, you put me at the head of the Far Probe project, and told me to direct everyone's attention away from Nemesis. I couldn't have arranged a close spectral analysis at that time, and since the Leaving - well, I haven't. But I will investigate the matter now, you can be sure.’

‘Let me ask you a question. Wouldn't it produce the same effect of motionlessness, if Nemesis were moving directly away from the Sun? It's a fifty-fifty chance whether it's moving toward the Sun or away from it, isn't it?’

‘Spectral analysis will tell us. A red shift of the spectral lines will mean there's a recession; a violet shift, an approach.’

‘But it's too late now. If you take its spectrum, it will tell you it's approaching us, because we're approaching it .’

‘Right now, I wouldn't take the spectrum of Nemesis. I'd take it of the Sun. If Nemesis is approaching the Sun, then the Sun will be approaching Nemesis, and we can allow for our own motion. Besides, we're slowing and, in a month or so, we will be moving so slowly that our motion won't be affecting the spectroscopic results appreciably.’

For the space of half a minute, Pitt seemed lost in thought, staring at his uncluttered desk, his hand slowly stroking the computer terminal. Then he said, without bothering to look up, ‘No. These are observations that need not be made. I don't want you worrying yourself about it any more, Eugenia. It's a nonproblem, so just forget it.’

The wave of his hand made it clear that she was to leave.

Insigna's breath made a whistling sound as it was forced out of angrily tightened nostrils. She said in a low husky voice, ‘How dare you, Janus? How dare you?’