The beeping did not stop when she opened her eyes.

It was a thin electronic chirp, steady as a metronome, and for three terrible seconds Sienna Hale lay with her cheek against something cold and flat and could not tell whether the sound was inside her head or outside it. She knew that sound. She had heard it a thousand times. She had never once been so afraid of it.

Then her lungs remembered their job. She dragged in a breath so violent it hurt, and shot upright.

The room swung, steadied, and resolved into pieces. White fluorescent tubes, humming. A steel bench crowded with racks of amber vials. A mass spectrometer in the corner, its status light blinking orange, chirping its complaint about a queue nobody had cleared. A paper cup of tea gone cold, the burnt corner of a slice of toast, and under her forearms the squared grid of a lab notebook, one page damp where her cheek had been.

The toxicology lab at Marenna General. Basement level two. Her bench, her stool, her chipped blue mug.

She was wearing a lab coat. Not a wedding gown. There was no Persian rug beneath her feet, only the scuffed gray linoleum she had mopped her own coffee off a hundred times.

Her hands flew up and patted her throat, her mouth, her ribs, the way a person pats their pockets for keys, searching for the thing that had killed her. Warm skin. A pulse thudding in her neck, hard and quick and alive. She held her fingers up in front of her face. They were warm. They were shaking, but they were warm, and the sight of them did something to her chest that she had no name for. A sound escaped her that was not quite a laugh.

"Hale?"

She spun on the stool so fast she nearly fell off it.

Nell Okafor stood in the doorway of the sample room with a lemon-yellow clipboard hugged to her chest and a frown of mild alarm on her face. Thirty-four years old, braids pinned up in a knot, reading glasses pushed into her hair and forgotten there. She was wearing the scrubs with the cartoon pears on them. In the life Sienna had just left, Nell had stood at the back of a cathedral in a borrowed green dress and mouthed you look beautiful across two hundred strangers, and Sienna had not been able to look at her, because looking would have meant crying in front of the Bellandis.

"You made a noise," Nell said slowly, "like a drowning cat."

"Bad dream." Sienna's voice came out rough. She cleared her throat and tried again. "Long night."

"Third one this week. Pryce is going to notice if you keep napping on his bench." Nell tilted her head, studying her with the kind of attention Sienna usually only saw her give to a suspicious chromatogram. "Also, the spectrometer has been screaming at you for ten minutes, and you've drooled on your notebook. That's not an accusation. It's a medical observation."

Sienna wanted, with a force that startled her, to cross the room and put her arms around her. She did not. She stayed where she was and gripped the edge of the bench until her knuckles went pale.

"Thanks," she said. "I'll clear the queue."

"Good girl. I'm doing the supply run. Want anything from the machine?"

"Coffee. Black."

"You are a monster," Nell said fondly, and went out, and the door sighed shut behind her.

The moment she was alone, Sienna snatched her phone out of her coat pocket.

The screen lit. 6:52. Beneath the time, in thin white letters, the date.

September 14.

She read it three times, the way she read every label before she touched a reagent. Then she opened the settings, because the lock screen did not show the year, and found it, and sat very still.

It was last year's.

She did the arithmetic twice, the way she double-checked every dilution, because a wrong number in her line of work could kill someone. Then a third time, because the someone might be her. Twelve months. Not roughly twelve months. Twelve months to the day. The wedding night, the champagne, the card under the white ribbon, all of it was still a full year away, and it would happen on this same date, September 14, in a room at the top of a hill she had never yet seen.

She was not dead. She was not dreaming. Or if she was, her dreaming mind had gone to the trouble of reproducing the burnt toast.

She pressed the heels of her hands against her eyes until colored lights bloomed behind the lids. When she lowered them, the lab was still there.

All right. Think.

A person who woke up certain they had lived the future had exactly two options. Either they were ill, or they were right. In her work there was only one way to tell the difference between those two: you made a prediction, you wrote it down in advance, and you let the world confirm or embarrass you.

She pulled the notebook toward her, flipped past the damp page to a clean one, and wrote the time at the top. Then she reached for the memory of this morning, the last life's morning, which she had not thought about once in the following twelve months, because it had been an ordinary morning and ordinary mornings leave no mark.

But they leave something. The mind keeps them in some deep, dusty drawer, and now that she pulled it open, small things spilled out into her hands.

7:10. Nell will drop a rack of buffer vials outside the door. Four will break. She will say a word she says when she thinks Dr. Pryce is not listening.

She wrote that down. Then, after a moment, her pen hovered over the paper.

7:48. Dad calls.

She wrote that too. She tried to add what he would say, and her pen stopped on its own, as if it had walked up to the edge of a cliff. She did not write the name. She looked at the two lines for a long time, and the room hummed around her, and the mass spectrometer chirped on, patient and indifferent.

Then she put the pen down and got to work, because it was that or come apart.

She cleared the queue first, because muscle memory is the last thing to leave a frightened body. Then she opened the drawer under the bench and took out a sterile needle, a collection tube, and a rubber tourniquet. She tied it above her elbow and pulled the knot tight with her teeth. She found the vein in the crook of her arm with two fingers and slid the needle in on the first try. She had drawn blood from patients a few thousand times. She had never once done it to herself with her heart going like a bird against a window.

The tube filled, dark and ordinary. She pressed a cotton ball to the spot, taped it, and spun the sample in the centrifuge. Then she loaded the broad screen and, after a hesitation, the narrow one too, the specific panel from the lab sheet she remembered so vividly from a case three years ago, the one with the cramped margin note in her supervisor's handwriting. Nobody tests for it unless they already know. Well. She knew.

Twenty-two minutes on the instrument. She set a timer and, because her hands needed something to do, took the penlight from her breast pocket and checked her own pupils in the dark glass of the reagent cabinet. Equal. Reactive. She counted her pulse against the clock on the wall. Seventy-four, regular. She pressed her palm flat against her sternum and felt it beating there, steady, unhurried, as though nothing had happened to it at all.

At exactly ten past seven, something shattered in the corridor.

It was a bright, sharp, unmistakable sound: glass on tile, once, twice, a scatter of small ones after. Sienna did not move. She sat with the penlight in her fist and listened, and into the silence that followed came a voice she knew better than almost any in the building, pitched low and heartfelt.

"Oh, bollocks."

The penlight slid out of her fingers and rolled across the bench.

She counted the shards under her breath, as they hit the floor, the way she would have counted anything. She did not need to. She already knew it would be four.

She made herself pick up the pen. Under the first line she wrote, in a hand that was almost steady: Confirmed. 7:10. Four vials.

The instrument chimed twenty minutes later, and she stood at the screen with her arms wrapped around herself, reading the numbers as they came. The broad screen: clean. No sedatives, no hallucinogens, no solvents, nothing that could have painted a year of memory across a sleeping mind. The narrow panel: clean. No trace of the compound that had stopped her heart on a ruined carpet. Her blood was the blood of a healthy twenty-six-year-old woman who had slept badly and eaten too little toast.

Clean, she thought, and then, with a small, cold shock: of course it is. It hasn't happened yet.

She sat down heavily on the stool.

There was a comfort in the clinical, and she took it with both hands. She made herself walk through the death the way she would have walked through any case on her bench. Not as her own death. As a sample.

Onset within minutes of the first sip. Peripheral coldness first, starting in the fingertips and going no higher than the wrists for a time. A bright metallic taste, like licking a coin. A tingling at the lips. The pulse slowing, not racing; that mattered. The voice going before the legs. No pain, which was strange, and no convulsions, which was stranger.

It read like aconitine. Monkshood, wolfsbane, the old poisoner's favorite. And it was not aconitine. She had watched aconitine kill a gardener from the third floor, and it had been uglier and slower, a long ladder of nausea and arrhythmia that showed on the standard screen as plain as a signature. What had killed her had been quick and quiet and had left a body that looked like a failing heart. Something dressed in aconitine's clothes. Something made by someone who had read the same textbooks she had, and then gone one chapter further.

That narrowed the world, a little. It was not a thug's poison. It was not a thing you bought in a harbor bar from a man with a gold tooth. It took patience and a clean workbench, or else a doctor's access to the kind of supplies nobody counts.

And someone had put it in a glass and set it on a sideboard in a room that had been empty while she hung up her veil.

She pulled the notebook to her and turned to a fresh page, because she could not think without writing. She drew a line down the middle and headed the left column Things I know and the right column Things I don't. Then she began, in small, hard, careful letters, the way she wrote up a case she meant to defend.

The sideboard was bare when the maid left. Twenty minutes later: ice bucket, bottle, white ribbon, two flutes, a card.

The ice had barely started to melt. Someone had been in the room only minutes before I came out.

M.B. read the card. M.B. put it in his pocket. M.B. did not tell me what it said.

The poison was in the glass, or the bottle. Not in the food, not in the cake, not in anything I tested all night. I tested nothing that evening.

She stopped, stared at that last line, and underlined it twice, with a vicious little stroke. In six years, not one meal, not one cup of coffee had passed her lips without a paper strip dipped in it first. She had gone to the altar with her kit in a handbag she did not carry. The only night of her life she had trusted a drink, someone had killed her for it.

In the right-hand column she wrote: Who set out the bottle? Who wrote the card? Why did M.B. hide it?

And then, below, so small it was almost an afterthought: Why was his glass empty?

Her pen stopped.

She had not meant to think about him. She had been very careful not to, all morning, the way you are careful not to press on a bruise. But now the thought came anyway, in full, with all its terrible detail, and she let it.

Matteo Bellandi, kneeling on the floor of the bridal suite with his shirt open at the collar and his hand pressed hard against her throat. The fine, fast tremor in his fingers. The color gone out of his face, and the voice that had been so low and measured all day cracking down the middle on her name. Look at me. Stay awake. Please.

She had seen that fear. She had looked directly into it. And she had spent a lifetime learning the difference between fear that is performed and fear that is felt, because her father was a man who could not stop performing, and she had grown up reading his face the way sailors read weather.

Matteo's fear had been real.

But real fear could mean so many things. It could be a man who had just seen his plan go terribly right. It could be a man who had not expected the poison to work so quickly and found, too late, that he could not watch it. It could be a man who had never meant for her to die at all.

The knuckle against her cheek. That was the part that would not stay put. One careful knuckle, easing a stray lock of hair behind her ear, so lightly she had barely felt it and so completely she had felt it everywhere. The way his hand had stopped. The way his face had come undone for one unguarded second, and she had thought, with perfect clarity, he is afraid. Not of her. For her.

A very long life, he had said. And meant it. She would have bet her own on that, if it had not been, in the end, the very bet she lost.

And at the last, when the room was going gray, he had lain down beside her. He had pressed his shoulder to hers and held her hand in a grip that hurt, and his lips had shaped one word she could read as clearly as print. Stay.

Sienna realized she had pressed her palm against her own cheek, where his knuckle had touched it. She snatched the hand away as though it had burned.

It was a stupid thing to feel, in the circumstances. It was a stupid thing to feel at all.

She pulled the notebook toward her and, at the bottom of the page, wrote: M.B.

She looked at it a long time. Then, because she was a scientist, because numbers were how she kept her hands from shaking, she added a figure beside it. 70%.

It was a ridiculous thing to put on paper, a number for a man's guilt. But seventy was honest. It was the part of her that had seen the empty glass and the shaking hands and the lie in the word safe, and it was also the part that had read a stranger's fear and believed it. She could not make the two halves meet. A man willing to drink his own poison was either desperate, or the most careful liar alive.

She turned to a fresh page and wrote across the top, in letters that were almost steady: DIVERGENCE LOG. Beneath it she wrote: Anything that does not match last time. Then, slowly, she added the first entry. 7:10, four vials, confirmed.

Then she sat back and made herself face the question that mattered.

What now?

She could run. The thought arrived whole, and she examined it honestly, because that was the only way she knew how to examine anything. A bus out of Marenna Bay. A new name in a town where nobody knew the sea. She had savings for six weeks of rent and a nursing friend in the north who would not ask questions.

And behind her, her father would stand alone in the old house on Tern Street with a debt that had a face and a temper. She had seen what that debt turned into. In the last life, it had turned into a wedding.

Besides, running would answer nothing. The poison had been served in a Bellandi house, in a Bellandi room, on a Bellandi sideboard. Someone had stood in that room with a bottle and a handwritten card, in the few unguarded minutes it took her to take off a veil. Someone had planned a death for her, wrapped it in ribbon, and known that two people would drink. A person who could do that was not a person who stopped.

She would never learn who it was by getting on a bus. She could only learn it by going where it had happened. And the only door into that house, the only door in the whole bright, glittering, bruise-colored city, belonged to the man she was most afraid of.

She let out a breath, slow and long. In for four. Hold for four. Out for six.

Twelve months. Three hundred and sixty-five days, more or less, until a night she knew down to the thread count of the carpet. She had never been so rich in time, or so poor.

At 7:48 the phone buzzed against the bench.

She did not have to look at the screen to know whose name it would show. She looked anyway. One word, in plain white letters. Dad.

She let it ring twice. On the wall, the clock said 7:48, and she thought of the line she had written on the clean page, and of the other line, the one she had not been able to finish.

She picked up.

"Sienna? Sweetheart, thank God. I know your shift's ending. I didn't wake you?"

"I'm awake, Dad."

"Good. Good." Edmund Hale had a voice like a worn sofa, soft and comfortable and sagging in the middle. This morning it was strung as tight as wire. "I need you to come to the house tonight. After work. There's something we have to talk about, and it can't wait. It's the Bellandis."

There it was. The name. In the last life it had been only a noise, a family from the hill, a word her father said in a whisper and she had not understood. It had sounded like nothing. It had sounded like weather.

Now it landed in her chest and she felt it spread all the way out to the ends of her fingers.

"What about them?" she heard herself say, and recognized every syllable. They were the exact words she had spoken the first time, the way an actress hears her own line from a play she has already performed.

"Not on the phone," her father said. "Please, Sienna."

She closed her eyes. Behind them, very clearly, she saw a hand with a gold signet ring reaching across a ruined carpet.

In the last life she had said, fine, I'll come, in the weary tone of a daughter used to bad news. She had walked into that kitchen unprepared. She had let the name in without a single question, and the name had walked her all the way to the altar, and the altar had walked her to the glass.

This time, she thought, she would not walk into any room unprepared.

"I'll be there," she said.

On her bench, the spectrometer finished its queue and, for the first time that morning, fell silent.