Rector was glad he’d let it go. “Good. I’m still a little on the feeble side, myself. I don’t suppose there’s an easier way up topside…?” he broached.

“Sure, if you want to get eaten by rotters.” But something about the way he said it was uncertain.

“Ain’t seen hardly any rotters,” Rector pressed. “I heard there was scads of ’em here, but Yaozu said there aren’t as many as there used to be.”

Swakhammer stopped, and although nothing of his face could be seen inside that amazing mask, his posture suggested that he was thinking about this. “There’s truth to that. At first I figured it was my imagination, but now I’m not so sure. It’s the order of the day, though—things disappearing. People disappearing.”

“I don’t understand…?”

“Mercy will tell you all about it. It’s not a coincidence, not anymore.” Swakhammer shook his head, as if this was a subject he’d rather not consider. So he said, “It’s not just the rotters. The population up there”—he gestured with his hands as though he was feeling around for the right thing to say—“It’s changing. The rotters are disappearing, but there are more birds, and the rats are coming back.”

Rector shuddered. “Rotter rats and birds?”

“No, not exactly. The air’s different for them, I don’t know why. It makes them sick, real sick—like mad dogs. But it doesn’t kill them. It doesn’t leave them roaming brainless and dead.” He shifted his shoulders and resumed course, waving for Rector to come along. “I don’t know how they’re getting in.”

“What if they’re getting inside the same way the rotters are getting outside?”

“Who said rotters were getting outside?” Swakhammer asked quickly. Even through the mask, reading between the mechanical lines of his speech, Rector thought he sounded entirely too innocent.

“Nobody. I just thought, if there were fewer rotters, they must be going someplace. And like you said, there’s no place for them to go. Except out.”

“You’re a real thinker, ain’t you?”

“Not usually. I’m just new here. Still learning the ropes.”

“You listen: If you ever think there’s a breach in the wall, you speak up, all right? We can’t have these things getting out. And it ain’t particularly good to have other things getting in.”

“Other things?” The shadow of a long-armed monster flicked through his memory, and he fought the urge to hug himself. “What other things?”

“Like I said. Birds. Rats. Dogs. Whatever. We don’t need ’em here. Don’t want ’em.”

Rector knew a white lie when he heard one, and he almost asked about the “inexplicable.” But Swakhammer didn’t intend to share anything further, that much was clear.