“Everyone thinks that the maintenance tunnels are the best way between districts,” Aijin told her as they walked. “They’re below ground, closed to the public, and they go pretty much everywhere. But actually, that’s kind of a trap.”

“What do you mean?”

“The access grates, like that one right over there, are pretty spread out. Like, there’s a quarter of a mile between each one, in any direction. You kind of commit yourself to a tunnel that had no cover, no ...