Slipping through the cleared drainage trough required keeping my shoulders pinned tight against the cold concrete. Once through the gap, my boots found immediate purchase on a narrow brick ledge bolted beneath the sill. I gripped the taut brass chain with gloved fingers, leaning back slightly to balance my center of gravity against the buffeting draft. Below me, an iron downspout curved neatly toward the outer fire escape platform. I planted the pick of my climbing axe deep into a weathered mortar seam to secure my secondary hold. Solid rock and iron ahead. The path downward is clear.