“The reason I gathered the three Partial girls was because I knew they might have something inside them, waiting to be unlocked. I thought it was the cure for RM, and I spent their entire childhood trying to find a way to trigger its release. That’s where I went last year—I found the facilities on Plum Island and used the equipment there to finish my research.” She held up the bag, staring at the small outline of a vial faintly visible in the folds of the fabric. “But the cure was never part of the genetic code for the new models, as Kira proved, and the trigger I found is for the disease.” She looked up. “If we give this to Isolde, she’ll start producing the pathogen in her lungs, and spread it to kill every Partial she comes in contact with.”

“Does she just drink it?” asked Kessler. “Does it have to be injected?”

“Injection only,” said Nandita. “The formula’s too fragile to survive the digestive system.”

“Why Isolde?” asked Ariel. She remembered all the lies and deceit and experimentation, an entire childhood as a secret lab rat in this woman’s hands. “Why didn’t you say me?”

“I thought you didn’t want to do it,” said Xochi.

Ariel roared at her without looking away from Nandita’s face. “Of course I don’t want to do it! But I want to know why she thinks I can’t.” She pointed at Nandita. “That wasn’t an accidental omission—you know something about me.”

“Your child died,” said Nandita. “Khan isn’t the first Partial-human hybrid, he’s the first one who lived; the plague processors in Isolde’s DNA made him immune to one disease, but cursed him with another. Your baby . . . simply died.”

“So you don’t think I have the Partial disease in my genes.”

“I don’t,” said Nandita. “I don’t know about Kira. Isolde, as far as I know, might be the only one.”

“So all the experiments,” said Ariel, “all the horrible things you did to us as kids, the herbs and the physical tests and the ‘alternative medicines’ you gave me to try to figure this all out, that was all for nothing? You treated me like a test subject when I lived with you, and a liar and a pariah when I tried to run away, and it was all for this? So I could just turn out to be completely normal, and everything you were looking for wasn’t even there?”

“Negative results are still results,” said Nandita. “You have more knowledge than you did before. More truth.”

“Yeah,” said Ariel. “The only true thing you’ve ever told me.”