Elara closed the PDF. “We stop reading it. And we write our own story about how we almost found the answer—but chose not to, for fear of what a recursive equation might decide about us.”

“It’s a textbook from the 1950s,” Leo said, stirring his coffee. “No offense, but it doesn’t even have color graphics.”

“Not the file. The equations. Chapter four, to be exact. The method of characteristics for quasi-linear partial differential equations. Sneddon derived them cleanly, elegantly. But the copy you found in the old server room? It was annotated. Not by me. By the previous chair, Dr. Amrita Khoury.”