An old mystery. As midnight strikes, a man desperately seeking sanctuary flees into a church. The next day, his sudden disappearance will make him famous throughout France. A new science. Forensic expert Enzo Macleod takes a wager to solve the seven most notorious French murders using modern technology - and a total disregard for the justice system. A fresh trail. Deep in the catacombs below the city, he unearths dark clues deliberately set - and as he draws closer to the killer, discovers that he is to be the next victim.