She took the ephemerides out of its cupboard and opened it to the back. He recognized where the precise writing of an unknown scribe ended and Liath’s began, full of ink blots, blurred letters, and sudden breaks.

“If we look at the progression of the planets through the ephemerides …” She turned, pointed, even though she knew the marks were meaningless to him. “On the thirteenth day of Cintre of the year 735, four of the planets will be in retrograde, moving backward along the ecliptic: fleet Erekes at the cusp of the Dragon, both sage Aturna and bold Jedu in the Lion, and stately Mok in the Penitent. This suggests lines of force moving in the universe against established patterns. Only bright Somorhas, shining as the Evening Star, moves forward and on this day enters the Serpent.” Her finger moved off the precise and rather fussy hand of the unknown scribe and onto the pages she had herself filled in over the last seven months. “But by the eighteenth day of Cintre, Erekes and Aturna and Jedu will reverse themselves and travel forward again, as if restoring the universe to its rightful order. Yet in the month of Setentre, two months later, bright Somorhas will go into retrograde, followed in early Octumbre by fleet Erekes. It all culminates on the tenth of Octumbre in the year 735. Aturna and Jedu will stand at the cusp of the Lion and the Dragon while Somorhas and Erekes move in retrograde through the Serpent and Mok slides in retrograde along the cusp of the Penitent and the Healer. The waxing crescent Moon, which by midnight will have set below the horizon, will be in the sign of the Unicorn. The Sun at midnight sleeps at the nadir of the heavens in the sign of the Serpent, the harbinger of death and change who shucks one skin only to live again newly reborn in another.” She lifted both hands, palms out to mark a point flatly made. “But we live in the northern latitudes. In the latitude where the Babaharshan magi lived in their ancient cities, on the tenth of Octumbre in the year 735 at midnight, the Crown of Stars will crown the heavens.”

“But that’s exactly what Wolfhere—” He broke off. Through the open door he heard the night breeze sighing through trees and, half hidden in the rustle of leaves, a scuff like that of a large animal moving along the ground. Mice skittered in the walls behind the open cupboard where the magi stored their apparati: an astrolabe packed in velvet in a rosewood case, an armillary sphere that showed the motions of the heavens, a celestial globe with the stars marked out as pinpricks of silvery paint. A shutter creaked. “That’s exactly what Wolfhere said to me.

She had to brace herself on the table either from another wave of pain or from the shock. “He lied to me,” she whispered. “He must have known she was here all along.”

“Liath—” He lifted a hand to warn her. A footstep pressed the earth outside. Jerna, hovering near Liath, suddenly darted away and folded itself into the metal bands of the armillary sphere until it became only a shimmer among shadows.

“You are wakeful,” said Anne as she crossed the threshold. She did not ask what Liath was doing; she did not need to.

“We commonly reckon a year by the return of the sun,” said Liath, not looking up. She still breathed hard, as after a footrace, and her gaze seemed fixed on some sight beyond the book that lay open in front of her. “The Babaharshan magicians reckoned a year by the precession of the equinoxes, when all the stars would have returned to the same places from which they had started out and by this means restored the same configuration over the great distances of the whole sky. One of their ‘years’ would count as tens of thousands of years as we reckon years.”

“You have been reading Cornelia again,” said Anne.

“But there might be other ways to reckon a year. By the cycle of bright Somorhas every eight years, for instance. Or by the Crown of Stars crowning the heavens.” Liath finally straightened. She looked tired, and anxious, and triumphant. “Some people say the Aoi were always here, before humankind built cities. Others say that long ago the Aoi sailed to these shores in beautiful boats woven of gold and silver reeds, and that they ruled over the villages of humankind and in time offered to teach some of them the arts of sorcery.”

“To their everlasting regret, when human magi turned against them,” said Anne. “When humankind outbred them and filled the countries the Aoi ruled with unmatchable human armies. When humankind brought disease to their masters, which they could not combat.”

Liath frowned. “According to the Book of Chaldeos, the emperors and empresses of the Dariyan Empire reckoned years as we reckon years, by each return of the sun. But they also imitated the Aoi, whose calendar recognized a Great Year equal to fifty-two of our years. Even Chaldeos didn’t know how the calendar of the Aoi worked. That was lost with them two millennia ago. But their year began and ended when the Crown of Stars crowned the heavens. They lived far south of us, or came from a land far south of where we live. They must have looked at the sky differently than we do.” Liath closed the book and set a hand on it, as if to keep it closed. Now she looked at Anne directly. “Who did the calculations in this book?”