Marlene had been running the numbers for three years. Not because she needed to run them — the numbers were simple, clean, the kind of arithmetic a child could manage — but because she kept hoping she had made an error somewhere. She had not made an error. One life for millions was the kind of equation that only became complicated if you had already decided that the one life was the wrong kind of variable.

Ellie had been brought to her as an infant, or something close to it. The details of the arrangement were not something Marlene thought about often, because thinking about them led to places that were not useful. What mattered was that she had watched the girl grow up from a distance that was careful, measured, professionally maintained. What mattered was that Ellie called her Marlene and not the other thing. What mattered was that she had already made her decision before the word cure had ever entered the calculation.

The Fireflies needed a win. They had always needed a win, but in the last eighteen months the need had developed an urgency that was beginning to look like desperation from certain angles. Salt Lake City was supposed to be the win. The hospital was supposed to be the win. And in a sense, it still was — the surgeon was confident, the immune response was understood, the procedure was straightforward. Only one thing stood between the Fireflies and the world they had been fighting for since before most of their members were old enough to remember the world that had been lost.

Marlene signed the order the same way she signed every order: without flinching, because flinching was a luxury that commanders did not get. She handed the paper to the surgeon and walked to the window and looked at the parking structure below where three armed guards were rotating shifts around a truck, and she thought: this is what leadership is. The ability to sign a paper and walk to a window and not think about what the paper means for the fourteen years that came before it.