“After twelve years, I’ve finally come to understand something,” said Vale. “Extinction has a way of making you choose sides,” said Vale. “I don’t want to hurt anyone, but if I can only save one species, I’ve made my choice.”

“It doesn’t have to be one or the other,” said Kira. “There’s a way to save both.”

“There was,” said Vale. “But that dream died with the Break.”

“You’re wrong,” said Kira, and she could feel tears welling up. “You, Armin, Nandita, and Graeme . . . all of your work was about this, about both races surviving. There must be something that I can do!”

“I promised you information,” said Vale, “and I’m a man of my word. Tell me what you need to know, and I’ll give you everything I can.”

They climbed the stairs to the hidden lab in the spire, and Kira considered the question: She had so many; where should she start? She wanted to know how RM worked, and what exactly the relationship was between the virus and the cure. If the same being produced both, how did they interact? She also wanted to know about the expiration date: how it functioned, how they might be able to work around it. Vale had been working on RM for years without cracking it, but he seemed to have no interest in the expiration date; he might know something valuable that he hadn’t followed up on yet. “Tell me about the expiration date,” she said.

“It’s really just a modification of my own work on the life cycle,” he said. “I designed the Partials to accelerate to a certain age and then sit there, freezing the aging process by continually regenerating their DNA. At the twenty-year mark, that process reverses, and the DNA is actively degenerated. They’re essentially aging a hundred years in a matter of days.”

“Samm didn’t say they age,” said Kira, “they just . . . decay. Like they’re rotting alive.”

“The effect is the same at that speed,” said Vale. “It’s not the nicest way to die, but it was the most elegant, biologically speaking.”

Kira furrowed her brow, still searching for the stray pieces to complete the puzzle. “How did you keep the expiration a secret from Morgan?”

“ParaGen was a maze of secrets,” said Vale. “Nobody trusted anybody else, and the board of directors trusted our primary scientists even less. That’s why we had to build two Failsafes.”

Kira raised her eyebrow. “Two?”