Professor Nash came back to work on Monday, and Mara was outside his office at nine with her thesis form.
He was thinner than before, and his collar stood away from his neck. A plastic pill box sat on his desk with the days of the week printed on the lid. Monday was already empty.
Eleven days ago, Mara had watched a clock over this man's head run down to twenty-nine seconds and stop. She couldn't stop herself from looking above his hair. There was nothing there.
"Miss Vance," he said, without raising his eyes from the form. "You've saved me a great deal of paperwork. If a professor dies on university property, it creates forms."
His daughter had come down from up north, he told her, just to watch him take a pill.
"I'm glad you're..."
"Yes. So am I. We don't need to go on about it."
He signed under Dina's name and Mara's, and held his pen over the title line.
"Evacuation Dynamics in Sealed Public Shelters," he read. "That's Miss Ashby's phrase. What's yours?"
Dina Ashby had written the title on the form, because Dina could make anything sound like it deserved a grant.
"Stairs," Mara said.
"Why?"
Mara had an answer ready, the one she'd given Dina, about the building code being thirty years old. It was a good answer.
Instead, she told him the real one.
"Nobody on Tannery Street was killed by anything that came over the wall. I read the inquiry."
The Tannery Street shelter had filled up in the Second Incursion, on the night the monsters got over the wall. Every first-year knew the number.
"Two hundred and six people died because of four steps down and a door that opened inward." She was talking too fast. She could hear it. "Somebody drew that door. Somebody checked the drawing. I like problems where, if it had been drawn properly, everyone would have gone home."
Professor Nash peered at her over his glasses. The pause went on so long she started counting the pills in the box.
"That's most problems," he said. "It's a heavy way to look at a drawing, Miss Vance. I don't say it's wrong."
He wrote the date and handed the form back.
"Chapter six. You still haven't read it."
'He nearly died a week and a half ago, and he still remembers my homework?'
***
Mr. Barrett kept the as-builts on the second floor of Municipal Works. As-builts were the drawings of what had really been built, as opposed to what was first designed. Most of Mara's job was finding where those two didn't match.
Municipal Works was a tired concrete block near the tram depot, with a wall levy notice taped inside the front door and a broken coffee machine on every floor. The drawing room had no window. One long lamp hung over a long table, and the drawings lived in steel drawers as wide as a door. The air smelled of old paper and pencil shavings.
Mr. Barrett was sixty-one. He wore a cardigan in every kind of weather and kept his glasses on a cord around his neck. He'd worked in the Shelter Section for thirty-four years, and he called the drawings "the sheets."
He brought out twenty rolls, one for each shelter on their list, and laid them on the table one at a time. He gave her the rules with them. The sheets didn't leave the building. They didn't get photographed. She copied what she needed by hand, and they went back in the drawer in the order they came out.
"Why can't I photograph them?"
"Because I said so."
He put his hand on the nearest roll, more gently.
"They're the only set, Mara. They're nearly as old as you are."
***
So for four evenings, Mara and Dina sat in that windowless room after everyone at the Section had gone home.
Dina came straight from her uncle's yard with the laptop and brick dust still on her sleeves. She took her boots off under the table and tied her hair up with whatever was in her pocket. On Tuesday it was a cable tie.
People who knew Dina from the cafeteria would never have recognized her here. She didn't chat. She built the computer model one shelter at a time, and for three evenings the only words out of her mouth were widths.
"One-ten."
Mara wrote it down. It was the fourth stair in a row at one meter ten.
"Who decided one-ten?" Dina asked.
"Someone with a tape measure that long."
Dina snorted through her nose and kept typing.
A cleaner's radio played two floors down. A tram ground around the corner outside every twelve minutes. Mara traced each staircase onto clear film, one flight at a time, and for whole hours nothing existed except what was on the table.
Nobody in that room had a number over their head. It was the calmest Mara had felt in weeks.
***
On Thursday, she needed one wall thickness.
In Shelter 131, the stairs shared a wall with the plant room, and the architecture sheet didn't give the thickness of that wall. So she unrolled the mechanical sheet instead, M-04. Every sheet had a letter. A was for architecture. M was for the fans, pipes and pumps. Mr. Barrett had given her the A sheets. She wasn't supposed to need the M sheets at all.
Three hundred millimeters. She wrote it down.
She should have rolled it up. She kept going, because one thing on the sheet was the wrong size.
The gray cabinet.
Mara had seen it in every shelter she'd ever walked into. It stood as tall as she was, bolted to the back wall, at the far end from the stairs, with a Medical Service seal on the front and one word under the seal.
PROPHYLAXIS.
The shelter dose. Spores drifted in from the Wilds on the east wind and made people sick. They'd first come with the Breach, years before Mara was born, the year the Wilds rolled over the land and the city built the wall. The wall stopped the animals. It didn't stop the spores, which was why everyone near it got the autumn booster.
A sealed shelter, with four hundred people breathing hard, was the worst place in the city to catch them. So when a shelter was sealed, the cabinet sprayed a medicine into the air, and everyone inside breathed it in at once.
On the sheet, the cabinet was drawn cut open. At the bottom sat a small tank, twelve liters. That was the dose. Above the tank was a chamber the drawing called a plenum, where fans pushed the mist out into the room.
Mara followed the plenum's outline with her finger.
It didn't stop where the cabinet stopped. It ran back through the wall, into a space she'd always taken for solid concrete. The size of that space was written in the corner of the sheet.
'Wait... so the cabinet is only the front door! To what, though?'
She did the division in the margin of her pad, and did it again underneath, to check.
"Dina. Check this."
Dina checked it. She didn't hurry.
"Forty," she said.
"Forty times the dose! And look at the fan. It's rated to empty the whole plenum into the room in ninety seconds."
"So it's big."
"Nobody builds anything forty times too big. It costs too much. You'd lose the contract."
"A backup? In case the first tank fails?"
"For a backup, you fit two tanks. You don't build one the size of a van and hide the back half inside a wall."
Dina rubbed her eyes with the heels of her hands. It was ten at night. She'd been awake since five.
"Mara, our project is the shelter stairs! It isn't tanks or fans, it's the stairs, and it's due in nine weeks."
Dina was right, and Mara knew it. They hadn't even finished measuring the stairs yet.
Mara pictured Shelter 131 on a siren night. The steel door shut. Four hundred people on the benches. The fan coming on, and ninety seconds of mist pouring out of a wall she'd leaned against a dozen times with a clipboard.
The title block sat in the corner of the sheet, the box that said who made the drawing. Architect. Structural engineer. The Shelter Section's own stamp.
Under those was a line she hadn't seen on the A sheets.
Mechanical subcontractor: Helix Adaptive Systems.
Next to it was the approval, dated twenty years ago, and a set of initials.
I.B.
Mara had never heard of the company. She wrote the name in the margin under her division and put a question mark after it.
'Helix Adaptive Systems. Who names a fan company like that? Fans don't adapt. Fans spin.'
She rolled the sheet up.
Before they left, she opened the M sheet for the next shelter. Only the title block.
Helix Adaptive Systems.
The one after that.
Helix Adaptive Systems.
Dina had her boots back on and her bag on her shoulder. She stood by the door and watched Mara unroll the corners, one sheet after another, and didn't say a word. Down the hall, the cleaner's radio had gone quiet.
Mara checked every roll on the table.
It was on all twenty.