“So it could go bite other foxes, and make them sick, too?” Houjin swung his bar up over his shoulder so it rested against his neck.

Zeke did likewise with his ax, and sighed. “Maybe if it got some fresh air, some regular air, it’d get better.”

They still whispered, though their caution evaporated somewhat in the wake of the fox’s disappearance. Rector still brought up the rear, watching backwards to make sure no one followed them, and praying that Houjin and Zeke would see anyone up ahead. It was odd, feeling so alone but knowing that they weren’t—that the city crawled with sick and dying things, and dead things that hunted regardless.

Rector surveyed the wall, too, but it stayed firm and showed no signs of holes, or even cracks. There were no breaches big enough to let anything person-sized (or even fox-sized, or rat-sized) in or out. He clung to it, oddly comforted by its epic reliability.

He said, “I thought maybe that fox was a good sign.”

Houjin looked back at him. His face was a masked shadow. “Why?”

“You saw it. It hadn’t been inside for very long. Makes me wonder if we’re close to the entrance, or exit.”

“But you saw it run off,” Zeke said. “Those things move pretty fast. It could’ve run pretty far.”

Huey paused, and the two boys who followed him paused, too. “What if we’re going about this the wrong way?”

“Everything feels like the wrong way, down here,” Rector said. He was getting thirsty, and he was also getting the very smothered feeling of spending too long in a gas mask. He wanted to get inside, someplace where the air was clean. He was running out of patience, and he didn’t want to admit it. It grieved him to think that the wall held several square miles of space, which meant that there was still a whole lot of territory to check before he could report to Yaozu that he’d done his job.

“That’s not what I mean. What if the hole isn’t in the wall—what if the hole is underground? Say one of the tunnels collapsed and left a spot that stretched beyond the wall, to someplace outside. What if things are getting inside that way?”

Rector snorted with exasperation. “Or what if they’re dropping from the sky, hitching rides on crows or dirigibles?”

“Don’t be like that,” Houjin groused back at him.

“Look, Yaozu told me to check the wall. He didn’t tell me to dig through every underground tunnel, pit, shaft, or cave. One thing at a time, all right? Let’s rule out the wall, and then move on to other ideas.”

Huey conceded, “That’s not the most unreasonable thing you’ve ever said.”

“God forbid you admit I had another good idea.”