A murder in the silent after-hour halls of the Louvre museum reveals a sinister plot to uncover a secret that has been protected by a clandestine society since the days of Christ. The victim is a high-ranking agent of this ancient society who, in the moments before his death, manages to leave gruesome clues at the scene that only his granddaughter, noted cryptographer Sophie Neveu, and Robert Langdon, a famed symbologist, can untangle.