Recovering from his injuries and the loss of Hélène, Balthazar flies home to Paris from Istanbul. When passengers start falling ill, he realizes they have been poisoned.

A freshly severed foot, a decapitated head and an innocuous man reporting his missing wife is just the start of one of the team's most disturbing cases.

A little girl is abducted from her room during the night and 24 hours later a ransom demand is made, but the truth behind the kidnapping is much darker than the team realizes. Meanwhile, Maya's presence continues to haunt Balthazar.

While investigating the brutal deaths of three young men, Balthazar is being audited by the forensic sciences institute and having to deal with Maya's continuing harassment.

During a lecture at the school of medicine, Balthazar and his team are held hostage by a student desperate to exonerate his father, who has already confessed to murder. Meanwhile, Camille continues meeting her mysterious friend.

Balthazar's lab is being filmed by a documentary team. Called to examine a skeleton found in the river, he continues to embarrass Vesinet as the police realize they're hunting a killer with an apparent taste for human flesh.

Balthazar is sent to his hometown to investigate the ritualistic killing of a cow and runs into memories of a childhood he'd rather forget. When former friends start dying, Balthazar's blackouts suddenly seem a lot more sinister.

Despite his friends' efforts, Balthazar refuses to defend himself. Believing there's no one he can trust, someone proves surprisingly helpful. Free from the drugs, he remembers a terrible secret but is it too late to fix everything?