“There are five. Two arctic zones, one at each pole. Two temperate zones, where humankind lives. And a single torrid zone along the equator, within which no creature can live.”

“Yet some live there nevertheless,” remarked Meriam pleasantly. “Tribes of humankind roam there, living in tents. Once it was said that sphinxes, the lion queens of old, made their home in the great desert.”

“They may have once,” retorted Marcus, “but they are legend now.”

“Many things are called legend which may still exist unbeknownst to human sight.”

Marcus laughed. “I am not as superstitious as you, Sister. I can only be sure a thing exists if I have seen it with my own eyes.”

“Have you seen God, Marcus?”

“God I must take on faith, but I would rather see Them with my own eyes, to be certain.”

Meriam smiled in her sharp way. “So may we all hope to do when we die, but not while living. Do not let the others hear you speak so heretically. Men have been burned for less.”

“You can be sure that I do not intend to be one of them.”

Summer had come and gone; the autumn equinox had passed, and now the course of days uncoiled inexorably toward the winter solstice. They had escaped Sordaia somewhat after midsummer and sailed south along the shore of the Heretic’s Sea to the harbor of fabled Arethousa. Zacharias had not been allowed to disembark, but he had stood for two days at the railing and stared in wonder at the great city on its hills while the ship-master had supervised the unloading of timber, furs, and wheat from Sordaia’s market and taken up wine, cloth, and iron knives.

In Arethousa, Wolfhere and Marcus had by unknown means received a desperate message that sent them southeast rather than west along the Dalmiakan coast toward Aosta. A strong wind called the halhim had delayed them along the Aeolian coast of the Middle Sea, forcing them to shelter for days at a time among its many pleasant islands until they had fetched up at an island the sailors called Tiriana, to rescue Meriam and her granddaughter.

That Meriam was a mathematicus needed never to be said aloud. Marcus informed the ship-master that they would detour to the port of Qahirah before returning to Aosta. Offered a bonus, the man did not demur. Perhaps, in truth, he was wise enough to see he had no choice in the matter. In the end, he served the skopos, who was rich and powerful enough to command him despite the physical distance between his ship and her throne. What mattered the intention in his heart as long as he did what he was told?

“Now,” said Marcus, “we will continue with the spheres. Earth lies at the center of the universe….”

Bit by bit, the architecture of the cosmos took shape before Zacharias, yet at times he wondered if it really matched that awesome vision he had seen years ago in the palace of coils. Remembering it, he still trembled, but he did not speak of the vision to Marcus, who cared nothing for the experience of others. Marcus knew what he knew, and that was enough for him.

Elene never joined them. She took her lessons, if she had any, privately with her grandmother. Otherwise, she stayed in her cabin or stood on deck, staring north and east toward the lands she had left behind. Often she had tears on her cheeks, but she never cried out loud.

“Is she always this sullen?” Zacharias asked Wolfhere one afternoon as he watched the sailors changing tack as the wind shifted.

“Have you heard her speak a cross word to any soul on this ship?” Wolfhere spent as much time as Elene staring out to sea, but not in any fixed direction. Zacharias was as likely to find him staring south as north, east as west.

“I’ve not heard her speak more than ten words altogether.”

“Well,” said Wolfhere, as if that settled the matter.

But it did not, for Zacharias wondered how any soul could not rejoice in the company of such learned mathematici. Yet when he asked Marcus the same question as he settled down for his next lesson, he got a very different answer.

“Ten words? Why should the daughter of a duke and the granddaughter of a queen speak even one word to you, Zacharias? You are of no account to an illustrious noblewoman born into such a distinguished lineage.”

“Of course you are right, Brother Marcus. But as she is heir to a duke, and granddaughter to a queen on her mother’s side, I am amazed that she could be torn from such a high seat and thrown like a common wanderer onto such a path as this one.”

“There is no path of greater consequence than the one we follow. Leave off these questions and attend.” Marcus stepped out from under the awning, shading his eyes as he gazed toward the cliffs, then shook his head impatiently and sat down again in the shade.