Kneeling in the first pew, Silas pretended to pray as he scanned the layout of the sanctuary. Saint-Sulpice, like most churches, had been built in the shape of a giant Roman cross. Its long centralsection—the nave—led directly to the main altar, where it was transversely intersected by a shortersection, known as the transept. The intersection of nave and transept occurred directly beneath themain cupola and was considered the heart of the church... her most sacred and mystical point.

　　Not tonight, Silas thought. Saint-Sulpice hides her secrets elsewhere.

　　Turning his head to the right, he gazed into the south transept, toward the open area of floor beyondthe end of the pews, to the object his victims had described.

　　There it is.

　　Embedded in the gray granite floor, a thin polished strip of brass glistened in the stone... a goldenline slanting across the church's floor. The line bore graduated markings, like a ruler. It was agnomon, Silas had been told, a pagan astronomical device like a sundial. Tourists, scientists,historians, and pagans from around the world came to Saint-Sulpice to gaze upon this famous line.

　　The Rose Line.

　　Slowly, Silas let his eyes trace the path of the brass strip as it made its way across the floor fromhis right to left, slanting in front of him at an awkward angle, entirely at odds with the symmetry ofthe church. Slicing across the main altar itself, the line looked to Silas like a slash wound across abeautiful face. The strip cleaved the communion rail in two and then crossed the entire width of thechurch, finally reaching the corner of the north transept, where it arrived at the base of a mostunexpected structure.

　　A colossal Egyptian obelisk.

　　Here, the glistening Rose Line took a ninety-degree vertical turn and continued directly up the faceof the obelisk itself, ascending thirty-three feet to the very tip of the pyramidical apex, where itfinally ceased.

　　The Rose Line, Silas thought. The brotherhood hid the keystone at the Rose Line.

　　Earlier tonight, when Silas told the Teacher that the Priory keystone was hidden inside Saint-Sulpice, the Teacher had sounded doubtful. But when Silas added that the brothers had all givenhim a precise location, with relation to a brass line running through Saint-Sulpice, the Teacher hadgasped with revelation. "You speak of the Rose Line!"The Teacher quickly told Silas of Saint-Sulpice's famed architectural oddity—a strip of brass thatsegmented the sanctuary on a perfect north-south axis. It was an ancient sundial of sorts, a vestigeof the pagan temple that had once stood on this very spot. The sun's rays, shining through theoculus on the south wall, moved farther down the line every day, indicating the passage of time,from solstice to solstice.

　　The north-south stripe had been known as the Rose Line. For centuries, the symbol of the Rose hadbeen associated with maps and guiding sou............