The temperature dropped a few degrees through the door, and even through her runners she could feel the change in the floor as it switched from linoleum to a rough patch of poured, cross-hatched concrete, and then to the smoother, older variant that occupied the rest of the halls. Up ahead, lights she hadn’t been able to reach during her earlier use of power cut across the end of the hall—bright, stark, and illuminating every subtle bow and dip in the floor for several meters before even thei...