Alan did not know the Starfall Observatory existed until Tuesday afternoon, when a lazy voice in his head gave him directions with the weary precision of someone who had walked there many times and had no intention of doing so again.

-- Third staircase after the herb garden, -- said Priscilla. -- Take the one with the missing banister. The door is not locked. It has never been locked. Nobody comes here because they believe it is haunted.

-- Is it haunted? -- asked Alan, climbing.

-- Only by me. -- A pause. -- I mean, by me in the past. I mean, in the sense that I once spent nine consecutive years in a room very like it. It is a very comfortable form of haunting.

The tower rose at the northern edge of the academy grounds, a tall round building of weathered grey stone with a cracked copper dome. Ivy covered its lower walls. A flight of crumbling steps wound up to a heavy oak door whose paint had peeled to a pale grey ghost of blue. Alan pushed it open, and a smell met him, dust and old paper and cold metal and something sharp and sweet, like crushed violets.

The room inside was round, and enormous, and very much in the process of being lived in. Bookshelves climbed the curved walls to a gallery that ran around the upper level, packed so tightly with volumes that some of them had given up and lay sideways on the floor. A great brass telescope pointed through a slit in the dome. Cushions of every color lay heaped on a worn rug at the center. Tangles of copper tubing, glass vials, and mysterious instruments covered every flat surface. Somebody, at some point, had drawn a mathematical proof on the floor in chalk and then given up halfway through the second line.

Alan stood in the doorway and, before he could stop himself, began to count the objects that were out of place.

-- Do not tidy, -- said Priscilla, in horror.

-- I was not going to tidy.

-- You were considering it. Your hand moved toward the inkwell.

-- It was crooked.

-- It is meant to be crooked. It is a deliberate crookedness. I have been cultivating it for decades. Come in. Close the door. Summon me.

He closed the door. He knelt on the rug, laid his palm against the dusty wood, and felt for the warmth in his chest. By now it was beginning to feel like reaching for a light switch in a familiar room. A pale violet glow bloomed between his fingers.

-- Priscilla, -- he said. -- Please come out.

The shimmer settled on the heap of cushions and, with a very small sigh, a woman lay down on it.

That was the only way to describe it. She did not step out of the light. She poured out of it, like a cat deciding where to sleep, and landed on her side with one arm tucked beneath her head. She was long and thin and curled like a question mark. Her hair was a great black cloud of loose curls, wild as a thornbush. She wore an enormous dark robe a good three sizes too large, its sleeves hanging past her fingertips, covered in a faint dusting of silver stars. A single round silver lens hung from a chain over one eye, slightly crooked, and behind it, her eyes were a deep strange violet that seemed to hold a small amount of light of their own.

-- Hm, -- said Priscilla, without opening them fully. -- Cushions. Good. I approve. Come here, specimen.

-- I would rather not be called that, Senior.

-- It is affectionate.

-- It does not feel affectionate.

-- That is a deficiency in your feelings. -- She waved a limp, sleeve-covered hand toward a low table that held a single glass vial full of a thick luminous purple liquid. -- Behold. I have been working on it for six hours. It stabilizes mana flow during the first week of a covenant. A mild tonic, in theory. You are going to drink it.

Alan crossed the room. He picked up the vial and held it up to the light. The liquid inside shifted in slow ribbons, like ink poured into water. It smelled, faintly, of violets and burnt sugar.

-- What is the risk? -- he asked.

-- The probability of survival, -- said Priscilla, with great cheer, -- is eighty-seven percent.

Alan lowered the vial slowly.

-- And the thirteen percent?

-- Mild distress. Possible hallucinations. A very small chance of temporary loss of sensation in the extremities. I would not call any of it fatal. Probably. -- She yawned, expansively. -- Drink up.

It occurred to Alan, in a sudden bright flash of clarity, that he had been waiting his whole life for someone to say a sentence like that to him, so that he could finally ask the right question.

-- Senior Priscilla, -- he said. -- What was the sample size?

Priscilla's yawn stopped halfway.

It froze, in fact, entirely, with her mouth still open. She lay motionless for two full seconds. Then she slowly closed her mouth, and turned her head, and looked at him with her violet eyes wide, behind the crooked silver lens.

-- I beg your pardon?

-- The eighty-seven percent. -- He held up the vial. -- It is a statistic. It has to come from somewhere. How many subjects did you test it on? What was the control group? How did you measure the outcomes? Is it an observed rate or a theoretical estimate?

-- ... Theoretical, -- said Priscilla, slowly.

-- Based on what?

-- Based on, ah. -- She propped herself up on one elbow. -- Based on my calculations of the potion's molecular stability.

-- So the sample size is zero.

-- The sample size is... -- Her eyes narrowed. -- The sample size is one, and it was me, and the results were inconclusive because I fell asleep.

Inside Alan's head, there was a sudden loud snort, instantly stifled, which could only have been Nyx. A second, deeper voice that sounded like Helga muttered, -- Finally. Someone asked. -- And a third, soft and warm and infinitely amused, said, -- Oh, I do like this boy.

Priscilla sat up. She sat up very slowly, as if rising from the bottom of a lake, and she looked at Alan for a long time. Her expression was not offended. It was something much stranger. It was the face of a person who had just been handed a gift she did not know how to open.

-- Nobody has ever asked me that, -- she said at last.

-- That is concerning, Senior.

-- It is, rather. -- She plucked at her sleeve. -- Usually people simply drink it or run away. Or, in the old days, they were administrative officials and wrote me a letter. I do not believe I have ever been asked for the methodology by a subject.

-- I think it is a reasonable request.

-- It is an extremely reasonable request. -- She looked down at her own hands. -- Hm. How very interesting. Give me that.

She took the vial, uncorked it, sniffed it, and a small guilty expression crossed her face. She put the cork back in.

-- I will not make you drink it, -- she said. -- Not yet. Possibly not ever. It was not as well characterized as I implied.

-- Thank you, Senior.

-- Do not thank me. It is a very low bar. -- She pushed the vial to the other side of the table with the toe of her slipper. -- But there is something else I would like to examine. If you permit it. Strictly speaking, it is the real reason I wanted you today.

-- What is it?

-- The structure in your chest.

Alan said nothing. His hand drifted up of its own accord and pressed against his sternum. He dropped it again, very quickly, and found that Priscilla was watching the motion with extremely bright eyes.

-- I have been wanting to look at it since the moment we were bound, -- she said. -- It is not any kind of lineage core I have ever seen. I could feel its shape from the inside. A ring. A hollow ring, like a bell with no clapper, vibrating in a frequency I do not recognize. Do you know what it is?

-- No, -- said Alan honestly. -- I have had it as long as I can remember. I have never examined it.

-- May I?

It was a very mild question, but there was something under the lazy tone, a tight, bright, trembling hunger, as if a very polite starving person had asked to look at the menu. Alan opened his mouth to say yes.

Then he stopped. He thought of the vial. He thought of the eighty-seven percent, and the sample size of one, and a boy named Alan Frost who had once said yes to everything, because yes was safer than a quarrel.

-- I would like to set conditions first, -- he said.

Priscilla blinked.

-- Conditions, -- she repeated, in a different tone, as if trying out the word.

-- Written conditions. If I am going to be a specimen, I want to be an informed one. -- He took a deep breath. -- I would like to write them down, and I would like you to agree to them. I would also like to say that if you do not wish to, I will understand, and we will find another way to proceed.

There was a very long silence.

-- I have lived for eight hundred years, -- said Priscilla, quietly, to the ceiling. -- I do not believe anyone has ever offered me a contract.

-- I can leave out the formal language.

-- Do not you dare. -- She sat up straighter, and a spark of fierce delight flickered in her violet eyes. -- Draft it. Give me paper. I will sign anything.

It took twelve minutes, and it was the strangest twelve minutes of Alan's life. He sat cross-legged on the rug with a sheet of paper and a pencil, and Priscilla lay on her stomach beside him, chin on her fists, reading each line aloud and commenting on it with obvious enjoyment.

-- Article one, -- Alan read. -- Consent. No experiment or measurement will be carried out on me without my prior knowledge and agreement.

-- Agreed. A bit stiff, but agreed.

-- Article two. Each procedure will have a stated backup plan, and a person present who is qualified to carry it out.

-- Seraphina, -- said Priscilla promptly. -- Whom I will be forced to be civil to.

-- Article three. Any party can call a halt at any time, for any reason. Mine is the word halt.

-- Hm. Reasonable. I will adopt it myself.

-- Article four. No secret experiments. No procedures conducted while I am asleep, distracted, or otherwise unaware.

Priscilla opened her mouth. Closed it. A faintly guilty look crossed her face.

-- That is a very specific article.

-- It is a general precaution.

-- ... Agreed, -- she said at last, and wrote her name at the bottom of the page in a large messy scrawl with an extravagant flourish. -- There. Signed. Duly witnessed by four unwilling spectators. You may begin.

-- Ouch, -- said Nyx, sleepily, from the back of Alan's head.

-- You are all very rude.

-- You have just read a legal agreement to a woman who calls you specimen, -- said Nyx. -- I am only noting the novelty.

Priscilla sat up and drew a small brass instrument out of her sleeve. It looked like a magnifying lens set into a ring of copper wire, and it hummed faintly when she held it up. She did not touch him. She held the lens in the air perhaps six inches from the center of his chest, and said, very quietly, in a voice that was not lazy at all:

-- Breathe normally. If you feel any pain, say the word.

-- Halt.

-- Good. Not yet. Breathe.

Alan breathed. The lens hummed. Beneath his shirt, the hollow in his chest began to glow, slowly, a pale circle of light that showed through the cloth like the glow of a coal through ash. It was not the bright white of the summoning circle. It was fainter, stranger, a soft silvery ring with a darkness at its center, as if someone had cut a perfect round hole in the fabric of the world and was holding it up to the light.

Priscilla did not speak. Her eyes were wide behind the silver lens, and her violet irises had begun to glow, faintly, like candles seen through a window. She lifted the brass ring a little higher, and the hum rose. The hollow brightened.

-- Oh, -- she said, very softly.

-- What is it?

-- It is, -- said Priscilla, and for the first time her voice lost its drawl entirely, -- not a core. Not in the ordinary sense. It is an absence. A very precisely shaped absence. A resonator. A chamber designed to ring, not to hold. -- She lowered the lens, but her hand was trembling. -- I have never seen one. I have only read about it. In a book. A single book. Which should not exist.

-- What book? -- said Alan.

-- ... I will tell you later, -- said Priscilla. -- When I am certain. -- She took a breath. -- I need to send a small pulse through it. Very small. A single measured thread of mana to see how it responds. It will sting. It will hurt me slightly too, because the backlash of any shared contact is divided between us equally. Do you consent?

-- Divided equally? -- said Alan.

-- Half to you. Half to me. It is a rule of this covenant. -- She tilted her head. -- It is a safeguard. It means no one of us can hurt the other without feeling it.

It struck him as a strange and oddly comforting thing, that an arrangement of five unfathomably powerful women and one very ordinary boy should have been built on the principle that no one could hurt anyone alone.

-- I consent, -- he said. -- Please be gentle.

-- I am never gentle. I am careful. It is much rarer. -- She lifted her hand. -- Ready?

A thin thread of violet light leapt from the tip of the brass lens and sank into the center of his chest.

It did not hurt, exactly. It was the sensation of a very fine needle being passed through a very thin piece of silk, a bright, thin, startling sting, and then a sound like a single bell struck in an empty cathedral. The silver ring in his chest rang. He felt it ring. A pure, round, hollow note vibrated through his ribs and out through his arms and into the stone floor. Dust jumped from the shelves. The telescope in the corner gave a small startled chime.

Priscilla gasped and clutched her own breastbone, and then, to his astonishment, laughed. It was a short, breathless, astonished laugh, the laugh of someone who had been handed a gift she had been looking for for centuries.

-- Oh, that is beautiful, -- she said. -- Oh, that is magnificent. Did you feel that? That resonance? The harmonic, the clean fundamental, no overtones at all. It is perfect. It is the cleanest tone I have ever heard.

-- It stung, -- said Alan.

-- It stung me too. -- She was still smiling, a little crookedly, and there were tears of laughter in the corner of one eye. -- It is the best sting of my life.

The glow faded. The ring dimmed and went quiet. The room was suddenly extremely still, and in the stillness, Alan realized that he was sitting on a cushion across from a woman who had been alive for eight centuries, who had decoded three thousand forbidden spells, and who was looking at him as if he were the most interesting thing she had ever seen.

It was the most uncomfortable and most flattering feeling he had ever experienced.

-- Mine, -- said Priscilla, very softly.

-- I beg your pardon?

-- My specimen. My exclusive specimen. -- She said it lightly, but something in her face was not light at all. -- No one else may touch it. No one else may measure it. If anyone so much as scratches you, they are damaging irreplaceable research.

It was clearly meant as a joke. It was also, Alan noticed, entirely sincere. Her fingers had curled around the brass instrument, and she was holding it a little too tightly.

-- That is, ah, a very strong claim, -- said Alan carefully.

-- It is a very strong specimen.

-- I am not sure that is a compliment.

-- It is the highest compliment I have. -- She pulled her sleeve over her knuckles and looked at the floor. A faint pink had crept into her cheeks, and her voice, when it came again, was quite a lot quieter. -- Nobody has ever asked me for conditions. Do you understand? It is a small thing. But it is not nothing.

Alan looked down at the paper in his hands, with its four neat articles and its large messy signature. He folded it carefully and tucked it into his pocket. His hand moved to straighten the edge of her cushion, which had slid sideways, and then to square the stack of papers on the table beside him, and then to align the pencil with the edge of the page.

-- You are doing it again, -- said Priscilla, softly.

-- Doing what?

-- Tidying. -- She watched his hands with steady, bright violet eyes. -- Every time you feel something you do not know what to do with, you arrange something. I have been counting. It is a very consistent pattern.

-- I do not feel anything. I am merely organizing.

-- It is, -- said Priscilla, almost to herself, -- an extraordinarily precise way to say that you do.

Alan had no answer to that. He stood up, brushed the dust from his knees, and began, with great dignity, to straighten the inkwell.

-- Crooked, -- said Priscilla, smiling.

-- It is meant to be crooked.

-- Yes. -- She leaned her head back against the cushions, and for the first time since he had met her, her smile was not lazy at all. -- Yes, it is.

The glow around her was starting to flicker. Alan felt the draw on his reserve tighten as the end of the session approached, and he took a breath and said, as formally as he could, -- Thank you, Senior Priscilla. For today. I will release you shortly.

-- Wait, -- said Priscilla.

He waited.

She lay very still for a moment, staring at the cracked copper dome. When she spoke again, it was in a voice that was not lazy or teasing or bright. It was low, and slow, and careful, and very quiet.

-- A hollow structure, -- she said. -- Shaped to resonate, not to contain. I have seen that shape before, Alan. I have seen it drawn in the margin of a manuscript written by a person I once knew. A person who is no longer here. It was only a sketch. A single line. But the curve was the same.

-- Whose manuscript? -- said Alan, and his voice came out smaller than he had intended.

-- I do not know, -- said Priscilla, and for a second she sounded as lost as a child. -- That is what troubles me. I thought it was his. I thought it was an idea of his, left unfinished. But now I think it was not an idea at all. I think it was a drawing of something that was already real. -- She closed her eyes. -- I will find out. I will not let anyone take that from me again.

The light faded. Her form thinned and dissolved into a cloud of pale violet motes, and the cushions on the rug settled into the shape of nobody at all. The observatory was silent. A single sparrow chirped on the window ledge.

Alan stood alone in the middle of the round room with his hand pressed against his chest, listening to the last faint chime of the ring fade from his ribs.

-- Tomorrow, -- said a warm voice from the front of his mind, soft as a hand on a forehead, -- is Wednesday. I have prepared herbal tea.

-- Thank you, Senior Seraphina, -- said Alan.

-- It is nothing, dear. -- A very small pause. -- I only wish to be certain you will arrive on time. You do tend to be so... easily distracted. By other people.

Alan looked at the empty cushions. He looked at the crooked inkwell. He thought of a violet-eyed woman on a pile of silk who had said, almost to herself, that nobody had ever asked her for conditions.

-- I will be there, -- he said. -- On time. I promise.

-- Good, -- said Seraphina. -- I will be waiting.