Where the water meets the stone.

I turned the phone toward the back wall of the vault.

A thin stream of water trickled down the limestone, dark and glistening.

It pooled in a small depression at the base of the wall.

I walked over to the wet patch, my shoes squishing in the damp soil.

I knelt down, ignoring the cold mud soaking through my trousers.

I began to feel along the bottom row of stones.

The mortar was soft and crumbly from decades of moisture.

I dug my fingers into the wet dirt, searching for anything solid.

Above me, through the thick ceiling, I heard a faint, rhythmic vibration.

It was the bass of the band playing in the ballroom.

The charity auction was about to begin.

My fingers clawed at the wet mortar.

The cold mud caked beneath my fingernails, stinging the small cuts on my knuckles.

Two rows down from the main seep, a square limestone block wobbled under my palm.

I pried at the edges.

The stone slid forward with a heavy, wet scrape, showering my knees with damp earth.