The scene at first was static, a fixed panorama of points forming a rough crescent. Every audience member knew it well. It was the local part of the spiral arm, complete with bright stars and diffuse clouds of dark or glowing gas. Builder artifacts were shown as minute flecks of vivid magenta. Nothing moved on the image, and the tension in the lecture hall grew steadily. When a green point flared suddenly into existence, there was a sigh from the whole audience.

“I suggest that you ignore that for the moment, and concentrate your attention here.” Bloom indicated a region of the spiral arm far from the green point, which had now spread to become a close-set pattern. Soon an orange speck of light flickered into existence, to spread in its turn and swallow up the green.

“Now, if you please, watch closely where the cursor is set. A new point — now! And its location: Earth, the original home of the human clade.” But Quintus Bloom had little need to speak. That source location was familiar to all.

So was the sequence that followed. One by one, other points brightened, moving out from Earth and Sol in a roughly spherical pattern. “Centauri, Barnard, Sirius, Epsilon Eridani, 61 Cygni, Procyon, Tau Ceti, Kapteyn, 70 Ophiuchi…” The names were spoken, not by Quintus Bloom but by the audience. It was little more than a whisper in the darkened hall, the ritual recital of the nearest stars that humans had explored at crawlspeed, before the discovery of the Bose Network.

The display continued: millennia of human exploration, shown in a couple of minutes. Bright sparks of a new color appeared, far off in the spiral arm. They too grew in numbers, until suddenly a thousand stars burst into light simultaneously.

“The discovery of the Bose Network, and the Bose Drive.” Again, Bloom’s comment was unnecessary. Everyone recognized the moment when humanity had exploded into the spiral arm at a rate limited only by the available ships and explorers, and human space had become linked with the sprawling worlds of the Cecropia Federation.

The dance of the lights continued. The orange points, which had winked out one by one, reappeared. But now the appearance of the spiral arm was no longer familiar. Myriads of stars glowed, in many colors. They extended across thousand of light-years, far beyond the boundaries of the Fourth Alliance, beyond the Cecropia Federation, past the farthest reaches of the Zardalu Communion. Suddenly everything was new, the familiar star maps swallowed up within a larger panorama.

“No longer our past. Our future, and the future of the other clades of the arm.” Bloom allowed the display to go on, spreading through the Arm and beyond, until at a gesture from him it suddenly vanished. He was left alone at the front of the stage.

“I know some of you had trouble with the idea, when I proposed a few minutes ago that the Builders are our own distant descendants.” His voice was conversational, even casual. “That’s all right. I had trouble myself, when it first occurred to me. But rather than trying to persuade you that I am right, I want to point something out to you, and let you make your own decision.”

Darya had the feeling that he was speaking directly to her. Certainly he was looking her way.

“The scenes you have just seen showed the spiral arm as it was long ago,” he went on, “and as it appears to be far in the future. Those images were taken from within Labyrinth itself. Now, is Labyrinth truly a new artifact, as I have suggested? Or is it merely one that we have managed to overlook for all these years? That is not beyond possibility, since it is small, and a free-space structure. Jerome’s World is the closest inhabited planet, but we are still over half a light-year away.

“We then have two possibilities: Labyrinth is new, and recently appeared; or Labyrinth has, like the rest of the Builder artifacts, been present for millions of years.

“Which one is the more likely? I began equally happy with either. But then I asked a question. Was it plausible that, three million years or more in the past, the Builders had been able to make a prediction — a precise prediction — of the way in which the clades would move out into the spiral arm? I do not think so. Ask yourselves the same question, and see what conclusion you reach.”

Behind Quintus Bloom, the moving tableau began again from the beginning. Earth was illuminated, then the neighboring stars. The Zardalu came and went; the Cecropians appeared. The audience could again follow that precise historical pattern of interstellar travel and development. The familiar expansion through space had a soothing, almost a hypnotic effect.

“If you believe that the Builders were, millions of years ago, able to make such devilishly accurate predictions, that’s fine.” Bloom was an invisible voice, lost within a sea of stars. “If not, take your thinking a little farther. Suppose that Labyrinth appeared recently — as recently as yesterday. Now, do you believe the development patterns we saw for the future? If you do, then we again face the same question: How can the Builders, today, know the precise pattern of expansion through the spiral arm as it will be hundreds and thousands and tens of thousands of years in the future? It is the same problem, merely displaced through time.”

The whole spiral arm was aflame with stars again. Earth had vanished, the Fourth Alliance was lost in an overwhelming sea of light.

“If you answer that the Builders had that magical power to predict the far future, then you assign to them talents that strain my belief past bearing. But if your answer is, the Builders are able to show such a pattern because it forms a part of their own past, then your thoughts agree with mine. The Builders are not three million years in the past; they are who-knows-how-many years in the future.”

Darya listened to the applause that filled the lecture hall at the end of Quintus Bloom’s seminar. She said not a word, in spite of the many heads turned in her direction. She knew what they wanted. Either a fight between her and Bloom, or agreement that his ideas explained what hers could not. She would not humor them. Science wasn’t a show-business talent search, conducted in large halls and decided by audience applause. Her time would come later, when she had the opportunity to probe Bloom for details and ask the subtle questions denied in the thirty-second sound bite of a public forum.

That chance would not be long in coming. Professor Merada always hosted a private dinner for visiting scholars after a seminar. Darya would be invited, even though she had just arrived at the institute. Her mouth watered at the prospect — and not because of the food.

Darya arrived a few minutes early. Professor Merada was already there, sitting as usual at the head of the table, with Quintus Bloom on his right. Normally Carmina Gold would sit on Merada’s immediate left. Tonight that had been changed. Darya circled the long table, seeking her own name card, and was surprised to find it right next to Merada, directly across from Quintus Bloom.

Bloom nodded to Darya, smiled at her reaction to the seating plan, and said, “At my request.” He went on talking to Merada.

Darya sat down uncertainly. Already, in some vague way, she was on the defensive. She studied the man across the table.

Seen close up, Bloom was not the attractive figure he had seemed on the stage. His face and neck were marred by some kind of skin disease, with coin-sized red sores only partly concealed by ointment and powder. His tongue seemed far too long. Darya watched with a revolted fascination as the pink tip flicked out far past his white teeth at every pause for breath.