The box answered every question.
Even when Sol put nothing inside it.
Mina had already sent the invitations. At three o’clock, twelve people would watch her machine open a message she believed no ordinary computer could read. After that, the laboratory would either give her another year or ask for its keys.
Sol stood beside the empty sample tray. His thumbnail was black from repairing the lift that morning.
“Seven,” he said.
“I can see the screen.”
“There’s nothing to measure.”
Mina opened the tray herself. It was a little metal drawer, lined with white cloth. The cloth held the square mark left by the sealed sample. Nothing else.
She closed it.
Seven glowed on the screen.
Her machine used particles that had only been discovered six years earlier. Each sealed sample had a paired sample in a second reader. Both readers had three settings: red, blue, and green. Turn both dials to the same color, and they were supposed to return the same number. Different settings produced useless noise.
That was the lock Mina had built for her teacher’s last message. The paper message was hidden behind a string of numbers. Only the paired readers, used in the order written in his notebook, should have supplied the numbers needed to open it.
She had made the new particles into a cipher: a secret code. She hoped it was a lock without a key anyone could copy.
Now an empty drawer knew its secret.
“Maybe the reader stored the last result,” she said.
Sol turned her dial to blue. He walked to the other end of the bench and turned the second dial to blue.
Eleven appeared.
“Last result was seven.”
“I know.”
He waited. He was good at waiting in a way that made her want to knock something off a shelf.
Mina pulled her teacher’s notebook close. Its cover smelled faintly of the coffee he’d spilled on it. A folded envelope was tucked inside the back cover, marked After the first public test.
She had not opened it. He had died before she completed the readers. She wanted to bring him an answer first, even if he would never hear it.
“You changed something,” she said.
Sol took his hand off the dial.
“I wrote every change down. You signed them.”
The laboratory director came through the door carrying three clean cups.
Venn liked to begin difficult conversations by offering coffee. He had brought cups without coffee this time.
“A small delay?” he asked.
“Possibly a stored number,” Mina said.
“Good. We can clear that.”
Sol laid the repair log on the bench. Two lines were circled in pencil.
The first recorded a weak signal from the second reader. The next recorded a wire joining its control board to the first reader’s board.
“The steadying wire,” Mina said. “You needed it to stop the display jumping.”
“You wanted it to stop jumping. I thought the wire only kept the two display clocks in step. I should have tried the empty drawer before I let you sign.”
Venn set down the cups, very carefully.
“I approved that wire,” he said. “A display we couldn’t read wouldn’t prove anything.”
Mina remembered the day. The number had flickered between seven and forty. Sol had asked for another week. She had asked whether there was a quicker repair.
Then she had signed his log and gone to order the invitations.
“Take it out,” she said.
“Power off first.”
“Then take it out.”
They stood in the room’s sudden quiet while Sol removed the wire. With both empty drawers closed, Mina turned the dials to green.
The first screen showed four. The second showed nineteen.
Blue gave nine and two.
Red gave forty and six.
Nothing matched.
She breathed out.
“That’s better,” Venn said.
Sol looked at him.
“It is,” Venn said, less firmly. “Now put the samples back.”
They opened the two drawers. Mina put the paired samples inside and closed them. For the next twenty minutes, the screens gave different numbers at every matching color.
The particles were still there. The matching numbers were not.
Mina sat on the stool meant for the first visitor.
“I need the wire,” she said.
Sol shook his head.
“I need to see what it does.”
He put it back. This time she watched his hands and wrote down the order of the settings herself.
Green: four and four.
Blue: eleven and eleven.
Red: seven and seven.
She removed the first sample. The screens still matched. She removed the second. They still matched.
Sol made a rough drawing on the back of an invitation. The wire carried the first dial’s setting to the second board, then carried the answer back. A program on that board returned a fixed number for each color. Both screens were showing the answer from that one list.
They had been watching one control board agree with itself.
Mina ran her fingers over the empty cloth in the drawer.
“It wasn’t a key,” she said.
“No.”
“It was a list.”
“Yes.”
The numbers in her teacher’s notebook had opened the hidden paper because he had chosen that same list when they first built the display. The machine had not proved that the particles could carry a secret.
She wanted to be angry with him. It would have been easier than remembering her own signature.
Venn checked his watch.
“We can postpone,” he said. “Tell them the lift failed. It nearly did.”
“And next week?” Sol asked.
“We explain when we know more.”
Mina looked up.
“Will I have the room next week?”
Venn did not answer at once. Outside, somebody rolled a cart past the door. One wheel squeaked every third turn.
“If the demonstration fails today, the board may give your time to someone else.”
“If it succeeds today?”
“They may pay for the repairs.”
He sounded tired. He wanted the laboratory to stay open. So did she.
Sol took his drawing away from the invitation and began copying it onto a clean page.
“What are you doing?” Mina asked.
“My report.”
His name went at the top.
His work was missing from every invitation. He had spent six months finding out what her machine actually did.
At three, Mina placed both empty drawers where the visitors could see them. She began with the test that had worked, including the wire. Then she removed the wire and repeated it.
The room became still when the numbers stopped matching.
A woman near the front raised her hand.
“Which result are you showing us?”
“Both,” Mina said. Her mouth was dry. “I signed off a repair that ruined the test. Sol found it.”
She put his drawing on the screen.
The questions lasted longer than the demonstration. One visitor left. Another stayed to ask Sol about the board. Venn collected the empty cups and did not look at her for a while.
Afterward, he gave her two afternoons a week for six weeks. She would share them with Sol. It was much less than the year she’d asked for.
Mina took the envelope from the notebook.
Inside was a photograph of her teacher beside their first crooked reader. On the back, he’d written, Tell me what it does when you give it nothing.
She sat with it until Sol finished sweeping the bench.
“Well?” he asked.
Mina turned the photograph over.
“We should have opened this sooner.”
Sol put the broom away. “We could have asked the box sooner.”
On the noticeboard, she pinned the photograph beside his circuit drawing. Under both, she added tomorrow’s first test.
Empty drawers. Wire out.
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