Silas gazed upward at the Saint-Sulpice obelisk, taking in the length of the massive marble shaft.

　　His sinews felt taut with exhilaration. He glanced around the church one more time to make sure hewas alone. Then he knelt at the base of the structure, not out of reverence, but out of necessity.

　　The keystone is hidden beneath the Rose Line.

　　At the base of the Sulpice obelisk.

　　All the brothers had concurred.

　　On his knees now, Silas ran his hands across the stone floor. He saw no cracks or markings toindicate a movable tile, so he began rapping softly with his knuckles on the floor. Following thebrass line closer to the obelisk, he knocked on each tile adjacent to the brass line. Finally, one ofthem echoed strangely.

　　There's ............