A Clue at the Valve

I tracked the baseline along the baseboard beyond the main pipe shaft. Four inches east, the metal line splits into a small drainage valve capped with a brass nut. Fresh scratches marked the painted trim right above it. I wedged my boot against the floor molding, gripped the ridged brass fitting with both hands, and leaned back to test the lock. Sealed tight. Then I noticed it: a small yellow thread caught in the threads of the nut. The fabric matches typical gear remnants. Bob definitely passed through this junction before moving lower.