Night Sentry on the Step

I pushed past the heavy stairwell door once more as night descended, stepping onto the cool concrete tread of the third step. A solitary stainless steel ball chain lay draped haphazardly over the grooved metal nosing. I planted my boots firmly on the gritty stone, took an upright stance, and gripped the lead bead. With steady, deliberate pressure, I pulled the chain until every bead formed a taut, unyielding line parallel to the step's edge. A discarded brass watch battery sat near the wall. I nudged it flush against the final bead to weight the terminal. Back against the riser, my night vigil begins.