As the second season begins, the police are searching for a missing child, after they discover a dead dog with traces of human blood. Although the officers soon suspect the child’s nanny, Balthazar comes to a different conclusion.

Balthazar analyses bones discovered in an old building and finds three bodies dating back to the Middle Ages, and one recent victim partially dissolved in acid.

Balthazar and Bach travel to a remote mountain village when a husband and wife suffer a knife attack that bears the marks of a serial killer who is supposedly in prison.

When a woman is found hanging from a bridge, it appears to be straightforward suicide, but Balthazar finds it strange that another victim died the same way days earlier after using a blind-dating site.

Balthazar locks himself inside a derelict toy store after he examines a body and determines that the victim died from an accelerated version of the bubonic plague.

After hearing an emergency call from a distressed teenager, Bach arrives at a crime scene with an empty car with smashed windows and a trunk full of snakes.

Balthazar and Bach finally track down a suspect in Lise's murder case, only to find he has been dead for 10 years and the real killer has been using the identity of the deceased; teenagers are butchered during a camping trip.

After receiving a threat from Lise's killer, Balthazar worries his new girlfriend, Maya, is in danger; Bach is called to investigate a body found in a pond, but the case turns personal when she realizes the victim is someone close to her.

Balthazar relies on drugs to numb the pain when Lise's killer sends him a video of her being murdered; a disturbed man wearing a woman's bloody scalp walks into the police station.