There was no turning back now.

I started down the steps, my boots making no sound on the thick layer of grime.

The air grew rapidly warmer, but it was a heavy, stagnant heat that smelled of wet dust, old oil, and rust.

With every dozen steps, the roar of the Chicago blizzard faded a little more.

Soon, there was only the sound of my own shallow breathing.

I reached the bottom of the stairs and shone my flashlight ahead.

The beam cut through a thick haze of suspended dust.

I was standing in a wide, circular junction chamber.

Massive brick arches supported the ceiling, the mortar crumbling into grey powder where water had leaked through from the streets above.

To my left, a set of rusted iron tracks ran into a dark tunnel.

I followed the tracks.

Water dripped from a pipe somewhere in the distance.

Plip.

Plip.

Plip.

The sound was steady, like a slow clock ticking down.

I kept my hand near my holster, my fingers brushing the cold steel of my Beretta.

I walked for five minutes, my flashlight beam bouncing off the curved brick walls.