“Heron’s tired,” said Kira. She was herself on the verge of tears, practically broken by Afa’s death. But she couldn’t quit now. She sat up to take the map from Samm and her own hand shook with the effort. “We’re all tired. We’re genetically perfect super-soldiers, designed to keep going under the harshest conditions, and we can barely move. We need to conserve our strength if we’re going to get to Denver.”

“Are you kidding?” said Heron. “You aren’t still planning on completing this idiotic mission, are you?” She turned to Samm, incredulous. “Samm, you know it’s time to do what we should have done weeks ago. Turn around.”

“If I’m right,” said Samm, “we’re barely a day’s journey to Denver. We could get there tomorrow.”

“And do what?” Heron demanded. “Find another ruined building? Risk our lives to get its generator running? Beat our heads against the computer because everything we want to look at is trapped behind firewalls and encryptions and passwords and who knows what other kinds of security? Afa was the only one who knew how to get past that; without him we don’t even know how to navigate the filing system.”

“We’re too close to give up,” said Samm.

“We’re not close to anything,” said Heron. “We’re going to go, and we’re going to find nothing, and this entire trip has been a waste of everyone’s time. We’re not going to cure RM, we’re not going to solve the expiration date, we’re not going to do anything but die in a wasteland.”

She lurched to her feet. “I’m not even going to say it.”

“Say what?” Kira demanded. “‘I told you so’? ‘We should have turned around after Chicago’? ‘We should never have left New York in the first place’?”

“Take your pick.”

Kira struggled to her feet, panting with the exertion. “You’re wrong. We came here with a job to do. If we don’t do it, Afa will have died for nothing. All of us will have. And we’ll take the whole planet with us.”

“Come on,” said Samm, but the girls ignored him. Heron reached Kira’s side before Kira even realized she was moving, and her fist slammed into Kira’s chin like a sledgehammer. Kira staggered back, already bracing herself to pounce back and attack before her mind had fully processed the punch, but before they could go any further Samm shoved himself between them. “Stop it.”