"This may take a while," Cal said, "because it is subtle."

"Too subtle for me," she murmured.

"I will explain it." He dusted off the clear plastic panel covering the tapestry storage chamber. This was unnecessary, for there was no dust. He brought out a small marking pencil.

"Where did you get that?" she asked.

"The marker? I've had it all the time."

She smiled ruefully. "He travels through Paleocene jungles, he battles dinosaurs, he tackles self-willed machines, he carries a cheap pencil."

Cal put his hand on her arm, squeezing. "Life does go on."

She turned her lovely blue eyes upon him. "Did you mean it, on Nacre?"

Nacre, fungus planet: There was no mistaking her allusion. Now he regretted that he had made reference to it in front of Veg; that was not kind. He looked into the depths of those eyes and remembered it with absolute clarity.

They had been climbing, forging up a narrow, tortuous trail between ballooning funguses and the encompa.s.sing mist. Aquilon, instead of resting, had painted -- not despite the fatigue, as she explained, but because of it. And though her subject had been ugly, the painting itself had been beautiful.

"You match your painting," Cal had told her, sincerely.

She had turned from him, overcome by an emotion neither of them understood, and he had apologized. "I did not mean to hurt you. You and your work are elegant. No man could look upon either and not respond."

She had put away her painting and stared out into the mist. "Do you love me?" Perhaps a naive question since they had only known each other three months, and that aboard a busy s.p.a.ceship; they really had had little to do with each other until getting stranded on the pearl-mist planet.

And he had answered: "I'm afraid I do." He had never before said that to a woman and never would again except to her.

Then she had told him of her past: a childhood illness that destroyed her smile.

Now she had her wish: She could smile again. That was the gift of the manta. But it had not brought her satisfaction.

"Yes, I meant it," he said. And did not add: But Veg loved you, too. That had formed the triangle, and she had seemed better suited to healthy Veg, especially on Paleo. Unfortunately the two had proved not wholly compatible and were in the process of disengaging. Cal hoped he had done the right thing in exposing Veg to Tamme. He had tried to warn Veg first, but the whole thing had a jealous smell to it as though he were throwing a rival to the wolves. Wolf, cobra -- by any metaphor, an agent was trouble. Unless, as with Subble, there was some redeeming human quality that transcended the mercilessly efficient and ruthless program. A long, long shot -- but what else was there?

"Look -- the pattern is changing! Aquilon exclaimed, looking through the plastic at the slowly moving material.

"Excellent -- the mantas have mastered the trick. Now we'll see how long it takes for a repair-machine to come."

"You were about to explain what you're doing."

"So I was! I am becoming absent-minded."

"Becoming?"

Such a superficial, obvious gesture, this bit of teasing. Yet how it stirred him! To Cal, love was absolute; he had always been ready to die for her. Somehow he had not been ready to banter with her. It was a thing he would gladly learn. At the moment, he did not know the appropriate response and would not have felt free to make it, anyway. So he drew three dots on the surface: "What do you see?"

"A triangle."

"How about three corners of a square?"

"That, too. It would help if you completed the square, if that's really what you want to indicate."

"By all means." He drew in the fourth dot: And waited.

She looked at it, then up at him. "That's all?"

"That's the essence."

"Cal, I'm just a little slower than you. I don't quite see how this relates to comprehension of the so-called 'pattern ent.i.ties' and travel between alternate worlds."

He raised an eyebrow. "You don't?"

"You're teasing me!" she complained, making a moue.

So he was learning already! "There's pleasure in it."

"You've changed. You used to be so serious."

"I am stronger -- thanks to you." On Nacre he had been almost too weak to stand, contemplating death intellectually and emotionally. He still had a morbid respect for death -- but Veg and Aquilon had helped him in more than the physical sense.

"Let's take your square another step," she suggested. "I know there's more. There always is with you."

He looked at the square. "We have merely to formulate the rule. Three dots are incomplete; they must generate the fourth. Three adjacent dots do it -- no more, no less. Otherwise the resultant figure is not a -- "

"All right. Three dots make a fourth." She took his marker and made a line of three: "What about this?"

"Double feature. There are two locations covered by three adjacent dots. So -- " He added two dots above and below the line:

"So now we have a cross of a sort." She shook her head. "I remain unenlightened."

"Another rule, since any society must have rules if it is to be stable. Any dot with three neighbor-dots is stable. Or even with two neighbors. But anything else -- more than three or less than two -- is unstable. So our figure is not a cross."

"No. The center dot has four neighbors. What happens to it?"

"Were this the starting figure, it would disappear. Cruel but necessary. However, the five-dot figure does not form from the three-dot figure because the ends of the original one are unstable. Each end-dot has only a single neighbor." He drew a new set: Then he erased the ends, leaving one:

"But what of the new dots we already formed?"

"Creation and destruction are simultaneous. Thus our figure flexes so." He numbered the stages:

1 2 3 4 "We call this the 'blinker.' "

She looked at him suspiciously. "You mean this has been done before?"

"This is a once-popular game invented by a mathematician, John Conway, back in 1970. He called it 'Life.' I have often whiled away dull hours working out atypical configurations."

"I haven't seen you."

He patted her hand. "In my head, my dear."