Ten years ago, Jacques Gaillard disappeared from Paris. No investigation has yet led to any clue as to whether he is missing — or murdered. Challenged to decipher the mystery once and for all, Enzo Macleod must use new science to crack a cold case. Once a forensics expert in his native Scotland, he's taken on a bet to solve seven murders listed in a cult book by an embittered Parisian journalist. Deep in the catacombs below Paris, a skull is discovered that could be Gaillard's. But it is the peculiar items embedded within the bone that give him the most intriguing clues — and send him on a trail after the rest of the missing man. Unaware that he's also following in the footsteps of their murderer...