When Lise's killer sends Balthazar a video of her being murdered, Balthazar relies on drugs to numb the pain and starts to lose his grip on reality. Meanwhile, a disturbed man wearing a woman's bloody scalp walks into the police station offering no explanation for his state.

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 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. Balthazar has little time to process his emotions before being pulled into a triple homicide investigation of teenagers butchered during a camping trip.

Balthazar examines a dead woman dressed as Snow White and determines she was shot, then buried alive. A USB drive hidden in her wounds reveals portraits of seven missing people, including the victim's son.

After hearing an emergency call from a distressed teenager, Bach arrives at a peculiar crime scene: an empty car with smashed windows and a trunk full of snakes. With little else to go on, Balthazar and Bach race to find the missing girl.

Balthazar examines a body at a derelict toy store and determines that the victim died from an accelerated version of the bubonic plague. Having been exposed to the virus, Balthazar locks himself inside to stop its spread, but will Bach's team be able to find the cure before he ends up another victim?

When a woman is found hanged from a bridge, it appears to be straightforward suicide, but Balthazar finds it strange that another victim died the same way days earlier. The fact that both victims had used a blind-dating site before their deaths points to a serial killer targeting women.

A husband and wife suffer a knife attack that bears the marks of a serial killer who is supposedly in prison. When Balthazar links the crime to a remote town in the mountains, he and Bach travel to the snow-covered village to determine whether the murderer is a copycat or still at large.

Balthazar analyzes a collection of bones discovered in an old abandoned building and finds three bodies dating back to the Middle Ages and one who died a week ago, partially dissolved in acid. The victim's girlfriend, who reported him missing, lives with her parents in a creepy house said to be cursed.

A dead dog covered in human blood leads police on a frantic hunt for a missing infant. Suspicion immediately falls on the child's nanny, who is not who she says she is, but Balthazar connects the case to a prestigious music academy instead.