Paris, 1830. In the heart of the town, Vidocq, a famous detective, disappears as he fights the Alchemist, an assassin that he has been pursuing for a few months. His young biographer, Etienne Boisset, decides to avenge Vidocq's death and takes the investigation on...

When the young detective Paul Nerteaux finds the third slashed female corpse of illegal Turkish immigrants, he decides to ask for support to the experienced dark retired detective Jean-Louis Schiffer to chase the serial killer. Together, they infiltrate in the Turkish mafia trying to find the answer to the crimes. Meanwhile, the worker Anna Heymes is being submitted to a brain treatment and has severe headaches and glimpses of memories and visions. When these two parallel events collide, disclose that the Turkish organization "The Wolves" is behind them.

In France, the single translator Diane Siprien adopts an Asian baby named Liu-San in a foundation directed by Sybille Weber. Years later, a weird mark appears on the boy's chest and Diane and Liu share their dreadful nightmares. Diane is assigned for a three-day job in Germany and she leaves Liu with her friend Sybille. However, while going to the airport, Diane finds Liu hidden in the backseat and startles with an eagle flying toward the windshield, crashing her car. Liu falls into a coma and his digital recorder records the boy speaking in an unknown dialect. When Diane searches the translation and the origins of Liu, she is surrounded by mysterious murders. She discovers that the dialect is from the mystic Mongolian Tseven tribe and that Liu is a powerful Observer; further, he is in danger, threatened by sorcerers that need the boy for their Council of the Stone..