The second harmonic did not return to the calibration console. It completed a circuit.
The fitted stone panels beyond the console folded inward. A circular settling shaft opened beyond them, its near ledge extending from the calibration alcove. A sloping wash corridor left that ledge and curved back toward the public freight drains. Straight ahead, a narrow iron inspection bridge crossed the shaft to a control gallery on the opposite wall. Its hinge, chains, and descending counterweight all sat on the gallery side, positioned to lift the entire bridge clear of the shaft.
Six recessed kennel doors surrounded the space. Three stood above the wash channel. Three more had been cut beneath the control gallery, their lower edges scored by claws.
Blue light left the three treatment plates and entered channels embedded in the stone. It crossed the open shaft, divided six times, and filled a brass tracking pane beside every kennel door.
