—Not somewhere, somewhen. Half a million years ago.

Could Kenna read her mind?

—No, but I understand what you need me to understand.

All of this was impossible; yet all of it contained an immediacy, a heightening of every sensation that told her it was happening.

—I’d forgotten my previous time here. Will I remember this one?

—Perhaps, but the part of your mind engaging in this conversation is not the part that controls your most conscious waking thoughts.

—Could you explain that more fully?

—Wait. We’re not all here yet. Ah . . .

The vacuum shimmered as if refracting light, rainbow spectra washed and flowed, and for a second Gavriela thought she saw two outlines, one of them odd - antlers? - then the other solidified into a crystalline man while the first was gone.

—Roger ?

—Gavriela?

Kenna stepped between them, reflections sliding across her body, looking from one to the other.

—You’ve interacted directly already? This is a good sign, my friends. And our comrade here is Ulfr, a warrior.

Roger held out his fist; Ulfr grasped his crystal forearm. Roger understood, and returned the clasp. Then he turned to Kenna.

—How can we be here now, and yet alive in the past?

To Gavriela this was impossible, despite her acceptance of the situation.

—Can our timelines criss-cross without paradox? I can’t see how.

It seemed obvious that if they communicated across time and remembered in the past, any number of paradoxes became enabled.

—Our meetings here will always occur in the same sequential order, as experienced by each of us individually. Call it a form of temporal tensegrity.

Roger was nodding, but Gavriela did not quite understand.

—I don’t . . .

—It’s a concept that will make sense in your personal future, else the thought would not have resonated at all.

That sounded like a paradox, except that their communication was not via sound; but Gavriela noticed how Ulfr had made a sign with his fist. Suddenly it came to her that Ulfr understood the words via his own frame of reference, using concepts that she would consider superstitious - because that gesture was to ward off evil, she was sure of it.

None of her own reactions were making sense. Why wasn’t she panicking, filled with hysteria?

Then Kenna added:

—No one in your lifetime will discover a basic equation that distinguishes future from past. Only the qualified generalisation you call the second law of thermodynamics even attempts the task, and it is not fundamental. There is no such thing as a closed system.

Gavriela blinked her transparent eyelids. For sure, if you described a particle’s motion via an equation, whether in mechanics or electromagnetism - such as a billiard ball floating through space - and then replaced t with minus t, you now had a picture of the same thing moving backwards, with time (or maybe just electric charge) reversed. The new situation would not appear to violate any physical laws; it would just run backwards. So the basic equations did not explain why you cannot unbreak an egg or grow younger by the day.

Roger touched Gavriela’s shoulder, and there was a spark of light, perhaps some odd reflection of the hall’s illumination.

—Don’t worry, I don’t understand either. And I’m alive much later than . . . Kenna, how can I know this? My life is centuries later than Gavi’s.

—You have good intuition.

—Is that an answer?

—It’s deeper than you think.

Gavriela looked at Ulfr. Clearly the warrior was content to stand apart from the conversation for now. Perhaps he considered it the realm of wizardry.

—Our brains are centuries in the past, yet we’re interacting with here and now. Is that what you’re saying?

—Partly, for sure.

—Therefore information is propagating backwards in time.

Kenna smiled at her and Roger.

—In terms that are common to both of you . . . If you stare at a star that is a hundred lightyears away, how long has that photon been travelling?

—A century, of course.

—And how much time has elapsed as far as the photon is concerned?

Gavriela checked for Roger’s reaction, but it was no more than a raised transparent eyebrow. Perhaps the new relativity of her time remained intact for Roger’s generation.

—No time at all.

—All that energy in the universe, more than the so-called matter, and it comprises splinters of timeless space. A photon is born and dies, travels perhaps across the universe, yet the duration of its life is zero.

That was what the equations said. Gavriela did not expect to understand the concepts intuitively, for she was a human being exploring realms beyond the macroscopic world, beyond the environment humanity evolved to cope with.

—How does that account for what we’re experiencing?

—It doesn’t, but symmetry is one of the most powerful concepts of all. Consider this possibility: splinters of spaceless time, orthogonal to photons. Call them orthons for now.

Gavriela shook her head, trying to incorporate the concept in her understanding.

—I need to think about it.

—That’s one way of formulating our interaction. At least part of it. Enough to work with for the time being.

Roger smiled. Perhaps there was more subtle humour here than Gavriela recognized. Or perhaps it was his different knowledge of physics that made his comprehension more sophisticated. If only she could learn from him!

Then her fear of paradox returned.

—We’re doing something dangerous here, aren’t we?

—Yes.

This seemed to be what Ulfr was waiting for.

—So what is our plan of battle, Lady Kenna?

—We devise a campaign, a war, not a single conflict . . . whatever it may boil down to in the final days. Have you identified the enemy?

Gavriela shared glances with Roger and Ulfr.

—Those touched by darkness?

—That’s part of it.

Kenna waved towards the table, but it was not an invitation to sit.

—We will share knowledge and strength, remembering some consciously. Our first task is to observe, to identify the enemy truly.

Ulfr was looking at the spears upon the walls.

—And then we fight.

This was scaring Gavriela. However much she accepted what was occurring, she was no fighter, and talk of warfare made her sick. Then she realized that Roger must feel the same way, as he asked:

—How? And what for?

But Kenna’s answer was directed more towards Ulfr.

—First we observe, then we deduce the enemy’s intentions.

Ulfr bowed his head.

—You speak wisdom, Lady Kenna.

Roger was looking at Gavriela, and she felt sure his thoughts followed hers. Of the three of them, it was this Ulfr who most closely accepted what Kenna was saying, and was most closely in tune with her intentions. Gavriela and Roger’s sophisticated understanding counted for little.

Perhaps Kenna sensed the same thing.

—We are all important. Every one of us.

—Are we?

—Immensely more than you think, good Gavriela. Immensely more.

Roger raised his crystal hands.

—So what do we do now?

—Why . . .

Kenna’s smile was a rainbow sculpture.

—You wake up, of course.

It was ended.

TWENTY-THREE

FULGOR, 2603 AD

In their quickglass bubble-capsule, they moved along a low Fulgor orbit - the planet fat and full, creamy-looking below them - heading for the apex of Barleysugar Spiral. Roger was lost in strange recollections of dreaming in Labyrinth, wondering whether the shock of being in another universe had done strange things to his brain, to his subconscious mind.