Now to those mysteries, add a third:

What was the nature of beings for whom the natural way to view a series of two-dimensional images was to stack them on top of another, in three dimensions?

Darya’s mind felt clear and clean, her body far away. Her suit was unobtrusive, quietly monitoring her condition and making automatic adjustments for heat, humidity, and air supply. She might have been back in her study in Sentinel Gate, staring at the wall and not seeing it, oblivious to sights and sounds outside the open window. At last a faint voice began whispering its message to her inner ear: Invert the process. Solve the third mystery, and its solution will answer the other two questions.

Darya cast her thoughts back over the years, to gather and sieve all the theories she had ever read, heard, or thought, about the Builders.

Old theories…

…they vanished over three million years ago, ascending to a higher plane of existence. The artifacts are mere random debris, the trash left behind by a race of super-beings.

…they became old, as any organism must grow old. Knowing that their end was near, and that others would come after them, they left the artifacts as gifts to their successors.

…they left over three million years ago, but one day they intend to return. The Builder constructs are no more than their caretakers, preserving artifacts on behalf of their once and future masters.

…the Builders are still here, in the spiral arm. They control the artifacts, but they have no desire to interact with other species.

And new theories…

…according to Quintus Bloom: The Builders are not part of the past. They are from the future, and they placed their artifacts in the spiral arm to affect and direct the course of that future. When key events reveal that the future is on the right course, the artifacts will change. Soon after that, the artifacts will return to the future from which they came. Those key events have occurred. That time of change is here now.

…according to Darya Lang: An idea sprang into existence, full-formed in her mind as though it had always been there. The Builders are not time travelers from the future. They lived in the past, and perhaps they live in the present. We cannot perceive them, and communication between them and us is difficult, perhaps impossible. But they are aware of us. Perhaps they also have sympathy for us, and for the other clades — because they are able to see the future, see it as clearly as humans see a scene with their eyes, or Cecropians with their echolocation.

They lived in the past… a race able to see the future…

Except that at any moment of time there could be no single, defined future. There were only potential futures, possible directions of development. Present actions decided which of those potentials would realize itself as the future, one among an infinite number of alternatives. So what did it mean, to say that the Builders were able to see the future? Was it more than a refined ability to perform extrapolation?

Put the question into more familiar terms: What did it tell you about the structure and nature of Darya Lang, that she was able to see? What physical properties of her eyes made her able to look close at a nearby flower (as the Builders were able to see tomorrow, in time), and then far off to a distant landscape (as the Builders could see a thousand years hence)?

Darya’s trance was complete. She sat at the brink of revelation, its message tantalizingly beyond her grasp. She saw in her mind the blurred, milky wall of the chamber, with its clear (but cryptic) three-dimensional message. Humans and Hymenopts could not grasp that message all at once, in its entirety. They needed to have it broken down into single frames, to see it a thin slice at a time.

But perhaps the Builders had no such need…

Darya sensed the first faint ghost of a different kind of being, one so alien in nature that humans, Cecropians, Hymenopts, and Lo’tfians — even Zardalu — were all close cousins.

If she were right, every one of her questions would be answered. The logical pieces were there. All she needed was confirmation — which meant more data.

She turned her visor to external viewing. “Kallik!”

She started, as the Hymenopt popped up right in front of her. Kallik had been waiting, eight legs tucked neatly beneath the round furry body.

“I am here. I did not wish to disturb your thoughts.”

“They were disturbing enough by themselves. Did you process the other five walls?”

“Long since. Like the first one, they exist now as sequences of images.”

“Can I see them?”

“Assuredly. I have reviewed one of them already. But with respect” — Kallik sounded apologetic — “I fear that it is not what you are hoping to see.”

“You mean it’s not a set of images of spiral arm clade evolution, the way that the first one was?”

“No. I mean that it is just such a set. It shows a representation of the spiral arm. However, it suffers the same problem as the one which we previously examined. By which I mean, it does not resemble what Quintus Bloom reported, and it is also quite inconsistent with what we know to be the true history of arm colonization.”

They were deep within Labyrinth, with no idea how, when, or if they would ever escape. Darya decided that she must be crazy. There was no other way to explain the sense of satisfaction — of delight — that filled her at Kallik’s words. She could not justify her conviction that she was going to achieve her life’s ambition. But she felt sure of it. Before she died, however soon that might be, she was going to fathom the nature of the Builders. She was already more than halfway there.

Darya laughed. “Kallik, what you have is exactly what I’m hoping to see. As soon as you are ready, I want to take a look at every one of those sequences.”

Any male Lo’tfian who has been removed from the home world of Lo’tfi and its breeding warrens is already insane. If a Lo’tfian slave and interpreter is also deprived of his Cecropian dominatrix, he becomes doubly mad. J’merlia, operating far from home and without orders from Atvar H’sial, had been crazy for some time.

Added to that, he now faced an impossible problem: Darya Lang had ordered him to look for a way out of Labyrinth. He had to obey that command. But it forced him to exercise freedom of choice, and to make decisions for himself.

A direct command to leave the others — and one that obliged him, for as long as he was absent, to operate without commands!

J’merlia was a mightily distressed Lo’tfian as he started out from the innermost chamber of Labyrinth. And, before he had gone very far, he was an extremely confused one.

In the short time since they had entered, Labyrinth had changed. The way back from the inner room should have led through a short tunnel into the chamber that teemed with the whirling black vortices. Vortices there certainly were, but only two of them, floating sedately against opposite walls. Neither one moved. Return through the chamber was trivially easy, as J’merlia quickly demonstrated.

The next one ought to have been as bad, with its fierce sleet of orange particles opposing any returning traveler. But when he got there, the storm had almost ended. The handful of little flecks of orange that hit his suit bounced harmlessly off and drifted on their way.

Logically, J’merlia should have been pleased; in fact, he became more worried. Even the walls of the third chamber did not look the same. They had dark windows in them, beyond which other rooms were faintly visible. There was also a translucency to the walls themselves, as though they were preparing to dissolve into gray vapor and blow away.

J’merlia went on. And then, just when he was wondering what unpleasant surprise he might find in the next room, he emerged from the connecting tunnel and saw a very familiar sight. Right ahead was the Myosotis, floating in the great helical tube, just as they had left it.