3. Glass Walls

The interrogation room smelled of stale coffee and recycled regret. Rei sat on a plastic chair that had been designed to be uncomfortable, facing two detectives who had not yet decided whether she was a victim, a witness, or a suspect.

Detective Nakamura was the older one, with a face like a crumpled paper bag and the kind of silence that made people confess just to fill the void. Detective Yoshida was younger, sharper, his eyes darting between Rei and the business card on the table as if the card might suddenly sprout legs and run away.

"Miss Kayama," Nakamura said, his voice flat as a dead sea, "do you know why you're here?"

Rei had already decided on her strategy. Partial truth, wrapped in confusion, seasoned with the exhaustion of someone who had not slept in thirty-six hours.

"A man named Julian Cross entered my office this morning," she said. "He threatened me. He showed me trading data that he claimed was part of an attack on a pharmaceutical company. I contacted the police because I didn't know what else to do."

Yoshida leaned forward. "You contacted us? We received an anonymous complaint from Cross Capital Holdings accusing you of unauthorized data access and potential market manipulation. They provided logs showing that you ran several complex scripts on your company's proprietary systems during off-hours."

Rei kept her face neutral. She had expected this. Julian had not only warned her; he had prepared the ground.

"The scripts were part of a personal research project," she said. "I was trying to understand a pattern of trading anomalies that I noticed in the data. I didn't manipulate any markets. I didn't execute any trades. I just ran simulations."

"Simulations that exactly matched the timing and volume of a series of sell orders on Daichi Pharmaceuticals this morning," Nakamura said. "Simulations that appear to have coincided with an unusually slow cascade of selling activity—slow enough that several large investors were able to exit their positions before the worst of the drop. Somebody made a lot of money today, Miss Kayama. And the timing was so perfect that our financial crimes unit is calling it either luck or insider knowledge."

Rei felt the trap closing around her, but she had anticipated this too. She had prepared a countermove.

"I sent the full data set to a journalist," she said. "A freelance investigator named Hasegawa who writes for the Keizai Shimbun. He has the tracing scripts, the transaction records, and the correlation matrix linking Cross Capital to three previous deaths. If I were trying to manipulate the market, I wouldn't be shouting it from the rooftops. I would be hiding it."

Yoshida's eyes widened. He exchanged a glance with Nakamura, who sighed heavily and rubbed his temples.

"You sent sensitive financial data to the press," Nakamura said slowly. "That's a violation of your employment contract at minimum. It could also be construed as a breach of financial secrecy laws."

"I'm aware of the risks," Rei said. "I accepted them because I believe that Julian Cross is responsible for the deaths of at least three people in this prefecture. I also believe he planned to add an eighth hundred this morning. I stopped that plan. I don't care about my employment contract. I care about the dead."

The silence that followed was thick enough to be cut with a dull knife. Nakamura stared at her with an expression that was not quite suspicion and not quite admiration—something in between, like a man who had just realized that the person he was interrogating might be telling the truth, and that the truth was going to be a bureaucratic nightmare.

"The journalist," Nakamura said finally. "Hasegawa. We'll need to verify your claim."

"He'll confirm it. But you need to move fast. Cross Capital Holdings is already scrubbing its digital fingerprints. I gave Hasegawa everything I had, but Julian Cross is not the kind of man who leaves loose ends. By tomorrow, the server in Singapore will be completely wiped. The shell companies will be dissolved. The trail will go cold."

Yoshida stood up abruptly. "I'll call the Keizai Shimbun. If this is a hoax, Miss Kayama, you're looking at criminal charges that will follow you for the rest of your life."

"Do it," Rei said. "And while you're at it, ask them to check the option data on Daichi Pharmaceuticals. Someone with a very large position in out-of-the-money puts made a fortune today. That someone is almost certainly Cross Capital Holdings. If you can connect the option purchases to the sell orders, you have a case for market manipulation."

She pushed the business card across the table. The handwritten words—Check your inbox—caught the fluorescent light like a taunt.

"He knows about you," Rei said. "He knows about me. He's been planning this for months. He didn't come to my office to threaten me. He came to test me. He wanted to see what I would do with the information. And now that he knows—now that I've shown him my hand—he's going to escalate."

Nakamura was silent for a long moment. Then he stood up, walked to the door, and called out to a uniformed officer in the corridor.

"Get me the financial crimes unit. Tell them I need a full audit of Cross Capital Holdings' East Asian subsidiaries. And find out everything you can about a journalist named Hasegawa at the Keizai Shimbun."

He turned back to Rei. "You're not under arrest, but you're not free to leave either. We have a holding room down the hall. I'd recommend you get some rest. You look like you haven't slept in a week."

Rei nodded. She stood up, and as she did, she felt her phone vibrate in her pocket. She had forgotten to turn it off. She pulled it out, glancing at the screen.

A new email. Unknown sender. Subject line: The grandfathers.

Her heart stopped.

She looked up at Nakamura, who was already striding toward the door. "Detective—"

"I'll see you in a few hours, Miss Kayama. Try not to do anything that makes my job harder."

He left. The uniformed officer escorted her to a windowless room with a cot, a sink, and a single fluorescent light that buzzed with the sound of trapped insects. She sat on the cot, her legs trembling, and opened the email.

It was short, like the first one. But this time, there was an attachment.

The attachment was a spreadsheet. It contained the names, ages, and brokerage accounts of seventy-two elderly men living in the Kita-Shima prefecture. All of them were over seventy. All of them had significant holdings in a single company: Kita-Shima Mutual Bank, a regional institution that had been founded in 1952 and had never once missed a dividend payment.

At the bottom of the spreadsheet, in a separate tab, was a series of transaction records. They showed that over the past six months, a series of small, unremarkable purchases had been made in the options market—put options on Kita-Shima Mutual Bank, all with a strike price that was 30% below the current market value. The options were set to expire in two days.

Rei did the math in her head. If the bank's stock collapsed by 30% in the next forty-eight hours, the option holders would make approximately three billion yen. And the bank would be forced to write down its capital reserves, triggering a run on deposits that would destroy the life savings of thousands of elderly depositors—people who had trusted the bank for decades, people who had no other assets, people who would be left with nothing.

She scrolled down to the bottom of the email. There was a postscript.

The attack was designed by my team, but the idea was yours. Do you remember the paper you published in 2022? The one about stochastic prediction in financial time series? I adapted your proof for the algorithm. You're not the hunter, Miss Kayama. You're the architect. You just didn't know it.

She stared at the screen. Her vision blurred, and she realized that she was crying—not from fear, not from anger, but from a deep, hollow recognition that made her chest ache with the weight of something she could not name.

She had written that paper when she was twenty-four. She had been proud of it. She had believed that she was contributing to a better understanding of risk, a more efficient allocation of capital, a world where financial markets worked for everyone. She had never imagined that her elegant equations, her careful proofs, her beautiful abstractions, could be used to destroy lives.

But they had been used. And she had been the one who provided the tools.

She closed the email. She lay down on the cot, her face pressed against the thin mattress, and she did not know whether she wanted to sleep or scream or never wake up again.

She did not sleep. She lay there, listening to the buzzing of the fluorescent light, and she thought about her father. She thought about the way he had looked at her when she explained her dissertation, the way his eyes had lit up with pride even though he had not understood a single word. She thought about the phone call she had received three years ago, from a hospital in Nagoya, telling her that her father had been admitted with chest pains. She had been in the middle of a coding session, and she had told the nurse she would come the next day. She had thought she had time. She had thought there would always be more time.

She had been wrong. Her father had died that night, alone in a sterile room, with no one to hold his hand. And the company that had taken his money—the renewable energy firm that had turned out to be a honeypot for foreign predators—had been financed by a shell that was later acquired by Cross Capital Holdings.

Her father had not been a victim of bad luck. He had been a victim of a machine. A machine that she had helped to build.

The door opened. It was Nakamura, his face pale and his mouth set in a thin line.

"Miss Kayama," he said, his voice tight. "We found Hasegawa. He was in his apartment when we arrived. He had been dead for approximately six hours. Coroner says it looks like a heart attack, but there are no witnesses and no signs of forced entry. His computer and all of his storage devices are gone."

Rei sat up slowly. The room spun around her, and she gripped the edge of the cot to steady herself.

"Julian Cross has been watching me for months," she said. "He knows everything I've done. He knows everything I've ever written. He knows how to use my own work against me. And he knows that if I try to stop him, I'll be destroying the very system I helped to create."

Nakamura stared at her. "Are you telling me that you designed the algorithm that killed those people?"

"No," Rei said. "I designed a theory. He turned it into a weapon. And now he's going to use it again—on the Kita-Shima Mutual Bank. In less than forty-eight hours, he's going to crash the stock and trigger a bank run that will destroy the life savings of thousands of elderly depositors. And I have no way to stop him."

She looked up at Nakamura, her eyes red and swollen.

"But I can help you catch him. If you let me out of this room, if you give me access to a computer and a secure connection, I can trace the option trades back to their source. I can show you where the money is going. I can help you build a case that will put Julian Cross in prison for the rest of his life."

Nakamura was silent for a long moment. Then he nodded slowly, almost imperceptibly.

"You have twenty-four hours," he said. "After that, I'll have to bring you in formally for the data breach. If you can't deliver, you'll be charged."

"I'll deliver," Rei said.

She stood up, and as she did, her phone buzzed again. Another email.

She opened it. This time, there was no text—just a single image attachment.

It was a photograph of Mrs. Yamada, taken from a window across the street from her apartment building. Mrs. Yamada was standing in her kitchen, making tea. She looked peaceful, unaware that she was being watched.

Below the photograph, in tiny text at the bottom of the image, was a caption:

You have forty-eight hours to stop the bank attack. Every hour you spend trying to catch me is an hour I spend watching her. Choose wisely, Miss Kayama.

—J

Rei's hands trembled. She looked up at Nakamura, who was waiting for her answer.

"I need to make a phone call," she said. "To my mother. And then I need to get to work."

She walked out of the holding room, her footsteps echoing in the empty corridor, and she felt the weight of the building pressing down on her shoulders.

She had twenty-four hours to stop an attack. Forty-eight hours to save Mrs. Yamada. And the rest of her life to figure out whether she was the hero or the villain of the story—or whether the story had become so tangled that the distinction no longer mattered.

The fluorescent lights flickered. Her phone buzzed again.

She did not look at it. She already knew what it would say.

The game was still on. And she was still losing.