“What gradient?” she prompted.

“Captains and engineers, plus the harum-scarums are among the highest souls,” he said. With a nexus, he sent her a complete list of species. “The most pragmatic species and jobs, as a rough rule. Of course the Remoras live even higher, outside the ship entirely, and they do sing a spiritual song … but the ones that I’ve actually met … well, they seem unconcerned by spiritual matters …”

“Spiritual?” Washen interrupted.

“Possessed of a mystical nature,” Perri offered. “In some ways, and it’s never a hard-and-fast condition.”

The First Chair had arrived here with one clear task in mind, and she was being ambushed by something else entirely. “You’re claiming that the deeper you move inside the ship, the more mystical its residents tend to be?”

“It’s a little something that I first noticed long ago,” Perri said, defending himself with a shrug. “Long ago, and now and again, ever since.”

Washen didn’t dredge up any of the voluminous research. Studies and census figures and the scholarly work by armies of xenobiologists had found only the slightest tendency, probably negligible.

“Mysticism is an inadequate word,” Locke warned.

“And there’s a lot of mud in any measurements,” Perri added. “Species have to be married to habitats, but the pragmatic captains decide which volume is going to be terraformed in what way. Plus there are gravitational needs, and economic constraints. And just because one species talks endlessly about gods and visions, you can’t accept the fact that they genuinely believe their own words—”

“Or that a pragmatic, concrete species is genuinely that way,” Quee Lee offered, finishing her husband’s thought.

Perri laughed.

And then Locke looked straight at his mother, saying the word, “!eech,” with a masterly voice. The exclamation point was a clicking sound, bright and loud, and the following “eech” was over in an instant.

No species had lived deeper inside the Ship than the !eech. Their habitat was inside one of the main fuel tanks, then it was abandoned. The captains had used their old home as their base before they journeyed to Marrow. As a species, the !eech had been xenophobes and deeply odd, and for the last many thousands of years, they had occupied one of those three hundred-plus positions on the official list of extinct species.

“It’s an interesting tendency,” Locke offered. “That’s all I’m saying.”

“What exactly are you working on?” Washen snapped.

Her son seemed very much like a young boy when he nodded, smiling shyly. “Species, present and lost. Interesting and unnoticed qualities about the ship. All those things Perri brings, and thank you, Mother. For putting us together.”

“Hyperfiber,” Perri blurted.

“What about hyperfiber?” Washen asked.

Locke nodded, focusing on some internal point that no one else could imagine. “Very possibly, the Great Ship is the largest single piece of hyperfiber in existence. Which is fascinating in its own right. But more important, I think … the hyperfiber surrounding us is billions of years older than any other example that we can envision …”

Washen felt her heart quickening. Why?

“Hyperfiber is hyperfiber because it reaches deep into hidden dimensions and shadow realities. That’s where it gains its strength, its nobility. Its perfection, and its quantum peculiarities.”

Quietly, Washen said, “I realize that.”

“But do you realize that the older it is, the greater its reach? According to certain mathematics, at least.” Locke lifted his hands, drawing nonsensical shapes in the dim yellow air. “This one great lump of hyperfiber … the majority of our hull and the supportive structures beneath, and the shell that surrounds Marrow … all of this has existed for twelve billion years, or more, each year of reality allowing its reach to expand into more shadow realms and other intellectual artifacts …”

“It isn’t any stronger because of that,” Washen pointed out.

“I’m not talking about strength,” her son replied, a hint of testiness in the voice. “I mean reach. And if the Great Ship was built when the universe was newly born … as you proposed, Mother, standing in the temple on Marrow … well, perhaps these hidden dimensions weren’t quite as well hidden back then. At the beginning of Creation, I mean. Which again makes for some interesting ideas.”

Washen knew enough to shiver but not enough to offer so much as a tiny suggestion. All she could do was stare at the yellowy glow of a bristle mold, and with a firm and pragmatic voice—a captain’s voice—she remarked, “Conjecture only gets us so far, darling. And if you don’t realize it, let me tell you: There may not be many more days before the ship isn’t ours.”

Three faces grew even more sober, sad and quiet.

It was Quee Lee who finally asked, “Why now, madam? Why are you here when so much else needs you?”

Washen lifted the tablet, piercing several deep encryptions before legible words finally began to form. “Just as the attack began,” she reported, “we received a short, repeating message. In an extinct language called Tilan, by the way. Which helps us authenticate the author. Who is Mere.”

The name was enough. No one breathed, not so much as a fingertip moved.

“It’s a brief message, and we managed to hear it repeated fifty-seven times. I don’t think she was certain that we’d hear her at all, and so …”For a moment, Washen lost her way. Then she smiled abruptly, surprising everyone, including herself. “I’m tired,” she confessed. Then after a deep sigh, she began to read the translation from the tablet. “‘once pond, only. No buds, only countless fingers.’”

Quee Lee glanced at her own soft hands. “Oh, goodness.”

“The Inkwell,” Locke muttered. “Is it a single Gaian?”

“Which makes sense,” Washen reported. “A lot of our evidence, some of which was sent home by Mere, points in that direction.”

“The slow ships moving neural matter from place to place,” Perri recalled. “They could be physical transfers of a shared mind, like electrical pulses between the cells in a brain.” He paused. “If the nebula is a single Gaian and it wants to function as so many little warm worlds, then it has to keep its bodies spread thin. Because if the pieces gather together—”

“Stars would form,” Quee Lee answered.

“Killing it,” her husband concluded.

Locke read his mother’s face. “But there is more. Am I right?”

Washen lowered the tablet.

“What else did Mere tell us, Mother?”

Stepping forward, she showed him the full text. With an appreciative expression, he studied the third, final line.

“What?” Quee Lee asked.

“It’s a tiny piece of a much larger equation,” Washen confessed. “By implication, I think Mere is telling us that this is what the polypond, the Inkwell, the one mind … this is what it believes.”

“Which equation?” asked Perri.

“It’s one of the Theories of All,” his new friend reported. Then Locke glanced up, staring at no one in particular, explaining, “This is one of those mathematical wonderlands that neatly explain everything just as well as their six good friends manage to explain it.”

“I thought there were just six Theories of All,” Quee Lee muttered.

“There’s always been a seventh,” Locke assured.

“It gets mentioned, on occasion,” said Washen. A deep memory surfaced for a moment, the face of her own mother appearing before her. “Engineers and most scientists don’t have any use for the monster, so they don’t bother mentioning it.”

“What exactly does it say?” Quee Lee pushed.

Everyone turned toward Locke.

“You know these shadow realms we talk about?” he began. “These parallel worlds and such?” He set the tablet facedown on the moist yellow ground. “In some theories, the parallel worlds are real places. In others, to varying degrees, they’re only shadows, ghosts buried in the big equations, and we are what is genuine, what is real. Our reality carries the rest along like a tree trunk holding up countless branches.”