“I wrote the first volume’s answer key,” Aris said flatly.

The last problem was typed in a font no one else seemed to notice—a perfect match for Lena’s old terminal.

He sent the manuscript to Mira with a note: “Vol. 2 is complete. I’ve solved the last problem. Don’t ask how.”

“The committee,” she whispered. “But they don’t exist anymore. Their last meeting was three years ago. On the same day your wife—”

The Last Equation

“Who?”

If he published the solution to Problem 12.7, every competition student in the world would learn how to decode the future. But they’d also learn how to reproduce the effect. The future war would bleed into the present.