Mother wanted to be downstairs.
She said it at breakfast, in the voice she used for things she'd already decided. The front room was warmer. The stove was there. She was tired of looking at the same four walls, and she wanted to hear the lesson.
"You can hear the lesson from upstairs," I said.
"I can hear you mumbling from upstairs. I want to hear the lesson."
Genny was already standing in the doorway with her sleeves pushed up.
She brought the bed down the same way she'd taken it out to the porch, turned on its edge at the landing, so smooth the water in the cup didn't move. Garnet rode on the end of it again, steering with her arms out like the prow of a ship, and made boat noises the whole way down.
Genny set it in the front room beside the stove, facing the kitchen door. From there, Mother could see the kitchen table, and the wall behind it.
The wall was the reason she'd asked.
Father painted the table the winter I turned six.
He'd spent a week on it. Mother said he did it at night, after I was in bed, with a lamp on the floor and a brush made from his own hair because none of the brushes he'd made from scratch would hold a straight line. When I came down for breakfast it was there, covering the whole kitchen wall from the counter to the window: a hundred and eighteen boxes in eighteen columns, each with a letter or two inside it and a number in the corner.
I'd thought it was a calendar.
It was the periodic table. Every element there was. Every kind of atom that the whole universe was built out of, lined up in order of how many protons they had in the middle, one after the next. Hydrogen in the top left corner. Then helium, all alone at the far right. Then lithium, starting the next row. All the way down to the big unstable ones at the bottom that nobody had ever made more than a few atoms of.
He'd painted the metals gray, the gases blue, the ones that liked to explode a hot orange. The ones he thought were important had little notes beside them, in his small square writing.
Beside carbon: Everything alive. Respect this one.
Beside oxygen: Everything burning. Also everything alive. Careful.
Beside uranium: No.
It was eleven years old now. The colors had faded where the morning sun hit it, and there was a dark smear across the noble gases where Garnet had once thrown oatmeal at Genny and missed. Nobody had ever painted over it. Nobody ever would.
I sat down at the table under it with Father's notebook number six open in front of me. The Table. His handwriting filled every page, and more of it crowded into every margin, notes on notes, arrows to other notebooks. Some of the arrows pointed to notebooks he'd never finished.
"Gold," I said.
Genny groaned.
"Gold is easy."
"That's why we're starting with it."
I took a lead fishing weight out of Father's old tackle box and set it on the table between us. It was the size of a thumbnail, dull gray, with a little hole through it for the line.
"Lead," I said. "Find it."
Genny rolled her eyes, got up, and touched the wall without looking. Bottom of the table, toward the right. Gray box. Pb. 82.
"Gold."
She slid her finger three boxes to the left. Au. 79.
"How far apart are they?"
"Three," said Genny. "Three protons. Take away three protons, and some neutrons so it stays together, and lead's gold. Everyone knows that."
"Everyone in this house knows that."
"Everyone who matters."
From the front room, Mother made a small sound that might have been a laugh.
"So why's it easy?" I asked.
Genny opened her mouth, then shut it again. She looked at the weight. This was the part she always skipped.
"Because it's just counting," Garnet said.
We both turned. She was sitting on the counter by the window, swinging her bare feet against the cupboard, with half a strawberry in her hand. I hadn't thought she was listening. Garnet never seemed to be listening, and she always was.
"That's right," I said.
"I know." She bit the strawberry. It crunched.
It was right. Lead was just lead, all the way through. Every atom in that little weight was the same as every other atom in it, lined up in the same plain way, like bricks in a wall with nothing between them. To make it gold, you didn't have to know anything about the shape of it, or what it was for, or how its parts fit together. You only had to change one number, the same way, everywhere at once.
"Gold is a word," Father wrote, in the margin of notebook six. I read it out loud. "Gold is a word. You only have to spell it once."
Genny sat back down. She pulled the weight toward her until it was well inside her foot, then put both hands flat on the table on either side of it and went still.
The weight shivered.
It was nothing much to look at. A little ripple across the gray. A sound like a breath let out. Then it was yellow. Not shiny yet, because the surface was dirty, but yellow all the way through, and heavier. You could see it settle into the wood.
Garnet slid off the counter and came to look. "Can I have it?"
"It's a fishing weight," said Genny.
"It's a gold fishing weight."
"There aren't any fish."
"There will be," said Garnet serenely. "On the moon."
Genny looked at me. I looked at the ceiling.
"Fine," said Genny, and pushed it across the table. Garnet took it into the front room to give to Mother, and I heard her explaining, in great detail, that it was a gold fishing weight for the fish that didn't exist yet, and that Lucas had promised.
"Now bread," I said.
Genny groaned again, louder.
I got up and went outside and came back with a handful of sand from the dry riverbed. I let it run out of my fist into a little pile on the table, next to the dent the gold had made.
"Sand," I said. "What is it?"
"Silicon dioxide," said Genny. "Mostly. Silicon and oxygen. One and two." She pointed at the wall without looking. Si. 14. O. 8.
"And bread?"
She started to point. Then her hand stopped in the air.
She looked at the wall. She looked at it for a long time.
"There's no box for bread," she said slowly.
"There's no box for bread."
Bread wasn't on the wall, because bread wasn't an element. It wasn't even one thing. I'd spent a winter on Father's notes about it when I was eleven, trying to make the tinned bread in the cellar taste like something. Bread was starch, which was sugar molecules linked in long chains, thousands of them, folded and packed together in grains. It was proteins, which were bigger and stranger and folded into shapes that mattered, and which stretched and tangled when you worked them, and held the air. It was water, trapped in some places and not in others. It was fat. It was salt. It was the leftovers of yeast, which had been alive. It was the crust, which was all of those things cooked a different way from the inside. It was the holes in it, which were nothing, but which had to be exactly the right size of nothing in exactly the right places.
It was carbon, hydrogen, oxygen, nitrogen and a little of everything else, but that told you as much about bread as the alphabet told you about a book.
"Gold's a word," I said. "Bread's a whole book. And you have to know every page before you can write it, or you just get letters in a pile."
Genny frowned at the sand.
"Have you done it?" she asked.
"Bread?"
"Real bread. Not the tin stuff."
I thought about lying. Father never lied to me about what I couldn't do.
"No," I said. "I've never had real bread. I don't know what it's supposed to be. I've only read about it."
Neither of them had either. None of us had. Everything we'd ever eaten had come out of the valley's dirt and Father's hands, or mine, or Garnet's. Strawberries we knew. Strawberries Garnet had made a thousand of. But bread was something people had in books, and in the domes.
Garnet came back from the front room without the gold weight. She looked at the sand on the table. Then she looked at me.
I knew that look.
"Garnet," I said.
"I'm just going to try."
"You can't make bread. Nobody here knows what it is. I just spent ten minutes—"
"I heard you." She scooped up the whole pile of sand in both hands, cupped it against her chest, and shut her eyes. "I'm going to think about it really hard."
"That isn't how it works."
"It's how strawberries work."
I started to argue and stopped, because it was true, and it was a thing I'd never been able to explain. Garnet didn't know what a strawberry was made of. She couldn't have told you one molecule in it. She had just eaten so many and made so many, and loved them so much, that her hands knew the shape of them better than any notebook. It was how I'd known water when I was four.
But she'd eaten a thousand strawberries. She'd never eaten bread.
The sand in her hands went dark and soft.
Genny leaned in. I leaned in. In the front room, the bed creaked, as if Mother were trying to see too.
Garnet opened her hands.
It was a loaf of bread.
It was a small one, round, about the size of a fist. It had a crust, golden-brown, cracked across the top the way the pictures in the old books showed. When she pressed it with her thumb, it gave a little, and sprang back. It smelled warm. It smelled like something none of us had ever smelled before and all of us somehow recognized.
"Garnet," Genny said, in a completely different voice.
Garnet beamed. She tore it in half. The inside was pale and full of tiny holes, exactly as it should have been.
She handed a half to each of us.
I bit into it.
It was sand.
Not gritty, like the strawberries. Not a bit like sand. It was sand. It crunched between my teeth like a mouthful of the riverbed, dry and flat and mineral, with a faint taste of bread somewhere very far behind it, like a smell from another room.
Genny had gone completely still, her cheeks full, her eyes watering.
Garnet took a bite of her own piece. Chewed. Stopped chewing.
"Oh," she said, with her mouth full. "That's not right."
There was a sound from the front room.
All three of us turned.
Mother was laughing.
She was laughing the way she used to, before. Not politely. Not the small, careful laugh she'd used for months now, so it wouldn't turn into anything else. This was the real one, the one that started low and helpless and took her whole body with it. She had her hand over her eyes. Her shoulders were shaking.
"Your faces," she said. "Oh, your faces. Garnet, darling, it's beautiful. It's the most beautiful sand I've ever seen."
Garnet spat her bite into her hand, looked at it, and started laughing too. Then Genny did, snorting, trying not to, with sand on her chin. And I did. Of course I did. The three of us in the kitchen under Father's wall, spitting sand into our palms, and Mother laughing in the next room as if nothing in the world were wrong.
Then the laugh caught.
I heard it happen. The exact moment. Her breath went in wrong, and the laugh turned over into a cough.
And the cough didn't stop.
I was beside the bed before I'd decided to move.
It went on for a long time. I don't know how long. Long enough for Garnet to stop laughing and come to the doorway with her hands still full of sand. Long enough for Genny to come up behind her and put an arm around her and turn her face away into her shoulder. Long enough that I stopped counting.
I held Mother up so she could breathe. That was all I could do. I had her by the shoulders, and she was so light, and I could feel every cough go all the way through her.
I could change anything I could see. I could see her lungs. I could feel them working, and failing.
I didn't know what to change them into.
When it stopped, there was blood on the handkerchief in her fist. Not much. She folded it over so it didn't show, the way she always did, and then she lay back against my arm with her eyes closed and breathed, carefully, like walking on ice.
"Sorry," she whispered.
"Don't."
"I ruined the lesson."
"You didn't ruin anything."
She opened her eyes and looked past me, through the doorway, at the twins. Genny's face was white. Garnet's was wet.
"Garnet," Mother said. Her voice was a thread. "Come here."
Garnet came. She dropped the sand on the floor as she came, and didn't notice.
"There was a bakery," Mother said. "In the dome. When I was a girl. On the ring street, by the east locks. An old man ran it. He used to put the loaves in the window at six in the morning, and the whole street smelled like it, and you could see the steam on the glass."
Garnet climbed onto the bed beside her, very carefully.
"It looked exactly like yours," Mother said. "Exactly. You got it right, darling. You got everything right except the inside."
"It tasted like sand," Garnet said, in a small voice.
"The inside's the hardest part." Mother's hand found Garnet's hair. "It always is."
Genny didn't come in. She stood in the doorway, holding on to the frame. I could see her measuring the distance from where she stood to the bed, the way she measured everything. Then she turned around and went back into the kitchen.
I heard her sweeping up the sand.
When Mother was asleep, I went into the kitchen.
Genny had swept up every grain. She'd put the sand in a jar, the half-loaves too, and the jar was sitting on the table under the wall with the lid screwed on tight. She was sitting in front of it with her hands in her lap.
I sat down across from her.
She didn't look at me. She looked at the wall. At the gray box marked O, oxygen, and Father's note beside it in faded paint. Everything burning. Also everything alive. Careful.
"Is she dying?" Genny asked.
She said it the way she said everything. Flat. Straight. Like a measurement.
I thought about all the ways I could answer that. I could tell her the doctors in the domes might have something. I could tell her I was reading the books again. I could tell her we'll see, the way I'd told Garnet in the field.
Father had never once lied to me about what was true. Not about the war. Not about the domes. Not about his own cough, when it started. He'd sat me down at this table, under this wall, and told me exactly what was happening to him, in words I could understand, because he said I deserved to know the shape of the thing I was afraid of.
I'd hated him for it at the time.
I'd been grateful every day since.
"Yes," I said.
Genny nodded once, slowly, as if I'd confirmed a number she'd already worked out.
"How long?"
"I don't know. Not long."
She nodded again. Her jaw was set. Her hands were folded very tightly in her lap, and her knuckles had gone white.
"Can you fix it?"
"No."
"Because you don't understand it."
"Because I don't understand it."
She was quiet for a long time.
"Then I'm going to learn it," she said. "All of it. Every notebook. So next time there's something like this, there's two of us who understand it. Not just one."
She didn't say next time it's me, or next time it's Garnet. She didn't need to. We both knew what ran in our blood, and what it did.
"Okay," I said.
She got up, took the jar of sand off the table and put it on the shelf over the stove, next to Father's lamp. Then she went upstairs without another word.
The jar stayed on that shelf for the rest of the time we lived in that house. Nobody ever asked why it was there.
That night, after they were asleep, I went to the cellar and got a new notebook.
Father had filled fourteen. They sat on the shelf over his desk in order, one to fourteen, their spines cracked white. Water. Air. Earth. Fire. That had been his joke, the first four. Then the real ones. Carbon. The Table. Metals. Living Things. Fourteen ended halfway down a page, in the middle of a sentence about protein folding, the week he died.
I'd never started a fifteenth. It had felt like his to start.
I sat at the kitchen table under the wall and opened it to the first page and wrote 15 in the corner, the way he had.
Then I wrote down what I didn't understand.
Bread.
Under that: Fish (on the moon).
I sat for a long time with the pen over the page. The filter hummed in the walls. In the front room, Mother breathed, carefully, carefully, and the stove ticked as it cooled.
I wrote: Mother.
Then I sat there until the lamp burned down, and I couldn't think of a single thing to write under it.