The virus did not kill everyone. It killed everyone over twenty-five. That was the elegant cruelty of it—a biological cut-off date, drawn not with ink but with CRISPR scissors and a mistake in a laboratory somewhere in Manhattan.

Evelyn Chen sat at the kitchen table of her sister's apartment in Brooklyn, staring at a whiteboard covered in equations. She was seventeen. Her parents had died in a car accident two years ago. Her sister, Rachel, who had raised her, was now asleep on the couch downstairs and would not wake up.

Evelyn had found her at 6:14 AM. Rachel's phone had rung at 6:15. It was the building superintendent, calling because he had noticed the silence. Evelyn answered because she was the emergency contact. She listened to the superintendent describe what he saw through the door—a young woman lying on the kitchen floor, breathing but unresponsive—and she said nothing. She simply hung up, walked downstairs, and checked Rachel's pulse.

It was there. Faint, but there.

Now it was 3:47 PM on a Thursday, and Rachel was still sleeping. So was everyone else in the building. So was everyone in the neighborhood. So was, apparently, everyone over twenty-five in the city.

Evelyn turned back to her whiteboard. The equations represented a resource allocation model she had been developing for her AP Economics project. It was supposed to model the distribution of municipal funds across five boroughs. Now it modeled something else: how to distribute 2.7 tons of canned food, 400 gallons of bottled water, and 180 liters of gasoline among 142 children in a three-block radius of Brooklyn.

The model had solutions. The solutions were not comforting.

"You're going to wear a hole in the floor," said a voice behind her.

Evelyn did not turn. She knew the voice. Marcus Webb was sixteen, had been expelled from three schools, and was currently the most powerful person in the neighborhood—not because he wanted to be, but because he was the only one who had figured out how to hot-wire a car.

"The model says we have forty-seven days," Evelyn said. "If we maintain current consumption rates."

Marcus leaned against the doorframe. He was eating an apple he had taken from the bodega on the corner. "Forty-seven days and then what? We starve?"

"We adapt. We find more resources. We—"

"Or," Marcus said, "we stop acting like we're running a goddamn corporation and just take what we need from the places uptown. The fancy supermarkets on Flatbush. They've got everything. Nobody's using it."

Evelyn finally turned to look at him. Marcus was not cruel. He was practical. There was a difference, and she was still learning where the line was.

"If we take from uptown, other neighborhoods will take from us," she said. "It's a zero-sum game."

"Everything's a zero-sum game, Evelyn. That's the point." He finished the apple and tossed the core into a recycling bin that had been sitting empty for three weeks. "What's the point of rules when there's nobody to enforce them?"

She did not have an answer. She had Nash equilibria and game theory and a spreadsheet that could optimize caloric distribution to within three percent accuracy. She did not have an answer to Marcus.

Priya Patel arrived at 5:30. She was fifteen, had won the state mathematics competition twice, and carried a backpack full of textbooks she refused to part with even though textbooks did not fill stomachs.

"I ran the numbers too," Priya said, dropping her backpack on the table. "Evelyn's right. Forty-seven days. Maybe forty-five if we account for spoilage."

Marcus frowned. "Forty-five? That's less than I thought."

"That's because you don't account for spoilage," Priya said. "Food goes bad. Water gets contaminated. You've seen what happened to the pool water at the community center. Green. Full of whatever was in those pipes."

Evelyn felt a familiar tightening in her chest. The numbers were solid. She had checked them three times. Forty-five days. After that, the model predicted a collapse of the current system—not a dramatic collapse, but a slow one, like a building settling into uneven ground.

"We need to expand our territory," she said. "Find other survivor groups. Establish trade routes."

Marcus laughed, but it was not a kind laugh. "Trade routes? You think people are going to trade with us? They'll shoot us."

"Then we make shooting less attractive than trading."

"By doing what? Sending them spreadsheets?"

Evelyn did not answer. She returned to her whiteboard and drew a new equation. This one was different—it was not about resources. It was about Marcus.

She had been tracking his behavior for weeks. Not in a creepy way. In the way a scientist tracks an anomaly. Marcus was unpredictable. He took food without asking. He hot-wired cars without permission. He challenged her authority not with violence but with a kind of casual contempt that was harder to fight.

"What are you drawing?" Priya asked, peering at the board.

"A variable," Evelyn said. "One that doesn't fit the model."

Marcus looked over her shoulder. "What variable?"

"You."

He stared at her for a moment, then smiled—not unkindly, but with something that might have been sadness. "Me. What about me?"

"You refuse to participate in the system I've built. You don't steal because you're hungry. You steal because you don't believe in the system at all. You told me yourself—you're not going to play by anyone's rules, even yours, because the rules are the problem."

Marcus was quiet for a long time. Then he said, "Maybe you're right. Maybe I am the variable."

"Then solve for me," Evelyn said. "Give me a number. Anything. How much food do you need? How much territory? What's your equilibrium?"

Marcus looked at her with an expression she could not read. "You can't solve me, Evelyn. That's the point. I'm not an equation."

He walked out of the apartment without another word.

Evelyn stood at the whiteboard for a long time. The equation she had drawn was unsolvable. She knew this the way she knew that 2+2=4. Some equations had no solution, and standing between her and the window, she could see the Brooklyn Bridge in the distance, its cables silhouetted against a sky that was too blue for a world that had just lost its adults.

Priya packed up her textbooks. "I'll come back tomorrow," she said quietly. "Maybe the numbers will be different."

"The numbers won't change," Evelyn said.

"But maybe we will."

When Priya left, Evelyn sat down at the kitchen table and opened her sister's laptop. Rachel had left a video message, recorded the week before she died. Evelyn had not watched it yet. She was afraid that if she watched it, Rachel would be gone in a way that the sleeping body on the couch could not capture.

She played it now. Rachel appeared on screen, smiling, tired, alive.

"Hey Evie," Rachel said. "If you're watching this, something bad happened. I don't know what. But I want you to know—whatever it is, you're going to be okay. You've always been okay. You just don't let yourself believe it."

Evelyn closed the laptop. She looked at the unsolvable equation on the whiteboard. She looked at the Brooklyn Bridge.

For the first time in weeks, she did not try to solve anything. She simply sat in the silence and let the numbers be wrong.