As midnight strikes, a man desperately seeking sanctuary flees into a church.

The next day, his sudden disappearance will make him famous throughout France. Forensic expert Enzo Macleod takes a wager to solve the seven most notorious French murders, armed with modern technology and a total disregard for the justice system.

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.