We found the first dead line without meaning to.

  One moment the terrace floor was a chaos of overlapping tracks; the next, they just… stopped.

  I almost missed it until my boot came down on unusually smooth grit. I checked my footing, looked back, and saw the difference.

  Behind us: dust churned, pocked, laced with tiny ridges where claw and foot and segmented belly had pressed.

  Ahead of me: an empty wash of powder, fine and even, like someone had taken a very large, very patient squeegee and dragged it across the floor—and then rinsed the squeegee in a field coil for good measure.

  I crouched at the boundary.

  The dividing line wasn’t perfect; this wasn’t lasers and tape. But over the space of half a meter, the story on the ground went from “crowded subway platform” to “clean room.” No scattering of pebbles, no abandoned shell fragments, no droppings.

  “Mercy,” I said. “Confirm I’m not hallucinating?”

  “Confirmed,” she said. “Local dust distribution ahead of your position has low-variance planar smoothness and low particulate disturbance. Behind you, it is noisy.”

  “That’s a very polite way to say ‘nothing walks over there,’” Frankie said.

  Chloe stepped up beside me, visor zoomed in to micro-level.

  “The dust layer depth is the same,” she said. “No different exposure time. Whatever’s smoothing it is periodic, not continuous.”

  “How periodic?” Trevor asked.

  “I don’t have a discrete timestamp,” Mercy said. “But density variance suggests a cycle on the order of hours, possibly days. There are faint subsurface stress patterns consistent with past high-energy passes.”

  “Translated,” I said, “something big comes through here occasionally and resets the floor.”

  “Or,” Chloe said quietly, “something up above does a cleanup. Sweeps.”

  Frankie wrapped his arms around himself in a full-body shiver he didn’t technically need.

  “So this is,” he said, “the part of the zoo path where it says ‘No Pets Beyond This Point’ and all the animals listened.”

  He paused, then scowled.

  “Rude,” he added. “I am technically pet hardware.”

  “You’re an emotional support firmware,” I said. “Completely different.”

  Trevor stood a meter back from the line, gaze fixed on the empty span ahead.

  “We mark this and we turn around,” he said. “We have enough data to log that something significant is happening inside that band. We do not need to be inside it yet.”

  Chloe chewed her lip.

  “We don’t know how wide it is,” she said. “Or what it’s for. If it’s genuinely quarantine, that might matter.”

  “Or it’s not protecting anything,” she added after a beat. “It just wanted its broken things repaired and cleared the rest out. We’re standing in the hallway where it doesn’t care what survives.”

  Support creative writers by reading their stories on Royal Road, not stolen versions.

  I hated how easy that was to imagine: the city fussing over our bruises and busted microfab while letting entire swathes of its own ecology get periodically erased.

  Mercy didn’t offer comfort.

  “Microfauna density drops by ninety-eight percent past that boundary,” she said instead. “There is no gradient. It is a hard edge. That is not consistent with avoidance behavior.”

  Trevor folded his arms.

  “Short incursion,” I said before he could argue with himself. “Three, four meters past the line, tethered, sled anchored on the safe side. Mercy watching the whole time. If we see anything that looks like ‘sweep cycle’ starting, we jump back and we log this as ‘do not enter.’”

  He shot me a look.

  I shrugged.

  “If this is a quarantine boundary,” I said, “I want to know which side we’re supposed to be on.”

  He exhaled through his teeth.

  “Fine,” he said. “Four meters. No more. And if Mercy says ‘back,’ we back.”

  “Already computing abort vectors,” she said. “I am not inclined to lose any of you to curiosity.”

  “Hey,” Frankie said. “Curiosity is literally my job description.”

  “It is not,” Mercy said. “You do not have a job description.”

  “Ouch,” he said. “Okay, that one hurt.”

  We anchored the sled to a railing post with two of the heavier stakes, double-checked tethers, and then, as a group, stepped over the invisible line.

  ?

  From inside the smooth zone, the absence felt louder.

  There was nothing obviously wrong with the architecture. The terrace continued ahead, curving gently along the dome’s interior. The railings were intact. The light-rivers along the walls still flowed, a little dimmer but present. A few doors studded the buildings to either side, outlines faint in the stone.

  But the air felt different.

  Not in any way my suit could quantify; Mercy’s atmosphere panel stayed a steady green. But some part of me that had been quietly tracking rustles and distant chittering ever since we’d arrived realized that the background noise had dropped.

  Less rustle. Less life.

  “Mercy?” Trevor said softly.

  “I am receiving fewer acoustic micro-events,” she said. “Part of that is distance from the more active terraces. But yes. Quieter.”

  Chloe brushed a gloved hand along the wall.

  “Same material,” she said. “No extra wear. Whatever does the smoothing is selective.”

  We edged forward.

  On the third meter, I saw the first gouge.

  It ran along the wall at about waist height, a double groove carved into the stone like something with two parallel blades had dragged along it under considerable force. Each groove had a faintly glossy interior, as if the passage had heated the material enough to seal the pores.

  “Okay,” I said. “That is not weathering.”

  Frankie stepped up, turning sideways to line his translucent arm along the mark.

  “This is at least three Frankies of problem, minimum,” he said.

  “Three and a half,” I said. “You’re underestimating your wingspan.”

  “That’s the nicest thing you’ve ever said to me,” he whispered.

  There were more gouges ahead.

  Some high, some low, some clustered at corners and doorframes as if something large had brushed them repeatedly while navigating the space. In between, the walls bore other scars: circular depressions with vitrified edges, patches where the stone had been melted and re-hardened in overlapping patterns, as if a storm of precision lightning had been pinned into rock.

  Mercy overlayed highlights on my HUD:

  POSSIBLE CONTACT SCAR – HIGH ENERGY

  PATTERN CONSISTENT WITH TARGETED DISCHARGE

  REPEAT INTERVAL: APPROXIMATE

  She traced invisible lines between the circular scars, mapping a repeating rhythm down the corridor, like some vast, invisible broom had passed through, sweeping sideways.

  “The gouges line up along a narrow band,” she said. “Roughly one-point-eight meters wide. Something long-limbed or field-extended moving through this corridor repeatedly.”

  “And the impact fields?” Chloe asked, voice low.

  “Not from the same source,” Mercy said. “Vectors are orthogonal. It appears that the city is… trimming.”

  She sounded reluctant to put a word to it.

  “Predator trail plus city cleanup,” I said. “Love that for us.”

  Trevor’s jaw tightened.

  “We are done here,” he said. “We’ve seen enough to know this is an active pathway for something large, and that the city periodically sterilizes it. We do not—”

  A flake of stone, loosened from some high scar by who knew what shift in humidity or minor field adjustment, chose that moment to break free and fall.

  It pinged off the rail near Frankie’s pendant and bounced toward the floor.

  The shell snapped around him so fast my eyes barely registered the in-between. One instant: Frankie standing there, expression halfway through an eyeroll. Next: his pendant dropping, hitting the floor, and blooming into that iridescent, armadillo-smooth stress shell.

  We all swore.

  The shell sat in the middle of the terrace, perfectly still, faint patterns crawling across its surface like slow waves in a forcefield.

  “New rule,” Trevor said through gritted teeth. “No loose debris near the experimental alien upgrades.”

  From inside the shell, Frankie’s voice came out muffled and offended.

  “I hate this mode,” he said. “It’s like being in a very smug egg.”

  “Stress parameter will clear in twelve seconds,” Mercy said. “Do not kick him.”

  “I was not going to kick him,” I said.

  “I was,” Chloe muttered.

  The shell’s patterns slowed, then reversed; plates unfolded, retracted, and Frankie snapped back into visibility with his hair a little more disheveled than before.

  “I am fine,” he said, dusting off imaginary dust. “Everything is fine. We are all fine. Please stop looking at me like that.”

  “We’re going to back out now,” Trevor said. “Mercy, mark the line of last safe contact.”

  “Marked,” she said. “I concur with retreat.”

  “For once,” Frankie said, “I am in complete agreement with authority.”

  We started the careful, definitely-not-panicked walk back toward the boundary.

  ?