Grid beneath the radiator

Descending from the iron baluster required four quiet paces across the cold concrete landing. Low clearance. No reverberation. Tucked beneath the cast-iron fins of a wall-mounted radiator, I found a dry, shaded recess perfectly concealed from the stairs above. On the dusty floor tile, a discarded cardboard delivery label was wedged flat against the wall skirt. Its surface displayed a dense square labyrinth of micro-blocks—a complex data matrix. I crouched low, pressing my curved arm against the cool iron pipe, systematically mapping the orientation of the tiny black and white squares. Unseen. Undisturbed.