The door to the backup return stair was hidden behind a frost-crusted iron grating set into the northern foundation wall of the headhouse.
Voss took his heavy pry-bar to the frozen hinges. He drove the forged steel wedge between the iron frame and the dressed granite cut stone. With three sharp blows of his sledge and a long, screeching groan of rusted metal, the iron gate popped free, shedding a shower of crystal-clear rime across the flat stone slabs. The smell that emerged from the dark sky-slit was not the dead, stale stillness of the main hoist column. But a cold, wet draft smelling faintly of crushed slate, copper salts, and ancient stone seep.
Behind the gate lay a narrow, barrel-vaulted hall that angled downward into the mountain at a thirty-degree slope. The ceiling was low—barely six feet from the flags to the keystone—forcing them to duck their heads as they entered. Thick rime coated the granite walls in delicate, six-sided crystals that sparkled like crushed diamond in their lantern beams. Every stone in the vault had been cut with drafted margins and keyed into the mountain with iron dowels. It was built by the old survey corps during the first fortification of the high pass.
