At six in the morning, Eren Tal knelt on the flat stone slabs of Zone Alpha with his ear pressed to the wooden handle of his two-foot framing square, the steel blade wedged firmly against the lead riser beneath the disconnected rinse basin. The washroom smelled of fresh wood shavings, hot boiled tea, and the crisp, yeasty aroma of sourdough crust rising in Sister Merrow’s ovens next door.
Pella stood beside him with the red Alpha stopwatch in one hand and her dark oak-ink ledger in the other. Along the wet stonework behind the tub, a fresh seam of gray pipe lime had crumbled onto the floor during the night, shaken loose by the steady fifteen-beat-per-minute tremor.
‘It’s not the tide,’ Eren said, sitting back on his heels and rubbing his stubbled jaw. ‘The morning flood slackened twenty minutes ago, and that knock hasn’t slowed by half a beat. You can feel it right through the soleplate. Three short taps, then a long drag like a timber barge scraping over a gravel shoal. Whatever is making that racket is coupled directly to the old cast-iron main under Fish Street.’
‘Listen to the gap after the third tap, Eren,’ Pella said, handing him her brass listening cone. ‘Tell me if you hear anything besides the scrape.’
