Jan Michelsen is investigating the disappearance of a young woman called Julie Vinding from a Copenhagen suburb. Six months later, Jan is the only one who believes that she is still alive. Jan finds a ten-year-old case from the same neighbourhood where a 17-year-old girl, Natasha, disappeared on her way home from a party. Jan discovers the remains of Natasha in a lake. She was murdered. Suspecting a link between the two crimes, Jan brings in an expert on serial killers, Louise Bergstein.

Jan and Louise’s investigation into Natasha’s death leads them to suspect Anders Kjeldsen, a man who has been arrested before for violent crimes including rape. Trapped in a basement, Emma tries to comfort a traumatised Julie, but soon needs comforting herself.

Jan and Louise find an unsolved murder case in Sweden that has similarities with Natasha's, although this one has an unusual signature: the victim's ring finger was cut off. Louise doesn't believe that the murder has been committed by Anders Kjeldsen. Meanwhile, on a farm that Anders Kjeldsen stayed at as a child, the police make a gruesome discovery. Stine is forced to help Anders with the women in the basement, who are planning to escape.

Louise realises that Anders Kjeldsen does not kill alone but has a partner who is the dominant of the two. In the basement, Emma tries to persuade Stine to help her to escape.

Jan and Louise find a dress belonging to Natasha – the first victim – which Anders Kjeldsen had hidden. That same night, Anders tries to kidnap another woman. Stine Velin attends her big brother Mikkel's 40th birthday party and reveals a dark family secret.

The public appeal for information on Anders Kjeldsen leads to the identification of the third victim from the farm and an explanation of how all the women met their killer. Louise suspects he has a female accomplice.

Stine Velin is taken into police custody, but insists that she is also one of Anders Kjeldsen’s victims and does not know where either Anders or Emma are.

Jan and Louise find Anders Kjeldsen. Louise fears that Stine’s family is in danger and places them in a safe house.

Five years ago, Alice Ejbye's 18-year-old son Markus was murdered by a serial killer who was never found. Alice is now seriously ill and asks criminal profiler, Louise Bergstein, the daughter of her best friend, to help solve the case. At the same time, elsewhere on Funen, a man named Peter Vinge receives a fatal message from his wife Masja.

A young man has been found in the woods, tortured and stabbed to death. Profiler Louise Bergstein and the head of the investigation Karina Horup try to find evidence for whether the murder can be attributed to a serial killer who, after a five-year hiatus, may now be active again. They slowly work their way towards the killer's highly unusual motive. Meanwhile, Peter Vinge struggles with being a single parent to his son, Johannes, and looks for his next victim.

Louise Bergstein and Karina Hørup discover that the serial killer has a claimed a new victim, William Fjeldby, who was kidnapped and abducted in his own car. William's father, multimillionaire Gorm Fjeldby, clings to the hope that his son has been kidnapped for a ransom and is therefore still alive. As the police search for William, Peter Vinge tries to celebrate Johannes's birthday without Masja. It dawns on Johannes that his father is hiding something from him.

Alice Ejbye receives some bad news from the doctor. At the same time, despite two new victims, the police have yet to find the man who killed her son Markus. Desperate, Alice posts a video on social media offering a reward which has consequences for her relationship with Louise. The police are inundated with information from people who are after the reward, and Karina and Louise struggle to determine whether there is anything useful among all the information. Peter takes his frustration out on his next victim.

Seven weeks after Alice's death, Louise is in mourning and wants to go home as Karina issues her with an ultimatum regarding the case. Alice's death raises a new suspicion which takes the investigation in a new direction. Peter Vinge focuses on his work at a local sawmill, where he receives an unexpected offer from Leif. At the same time, Peter is in conflict with Johannes who remains in a stage of teenage revolt against his father.

Louise Bergstein continues to assist the investigation to find the serial killer, who now has six brutal murders to his name. With Karina Hørup, Louise returns to the first victims in an attempt to find out where they may have met their killer. Peter notices that the police are closer to him than ever before, and at the same time happens to meet Louise again.

Unaware of who he really is, Louise gets far too close to Peter. But the terrible truth lurks beneath the surface. Karina tries to find new evidence for the investigation on her own, and an earlier clue resurfaces, moving the case forward. Peter sorts his life out and gives Johannes a message that his son has a hard time coming to terms with.

The police take Johannes to the station, and Louise fears that the truth about her and Peter Vinge will be revealed. Meanwhile, Peter meets his ex-wife Masja, who has returned from Singapore without notice in order to set things straight. Karina, Søren and Torben desperately try to find Peter before he can claim another victim.

Louise is determined to continue working as a profiler and when a couple is found brutally murdered, she takes on the case. She assists Detective Inspector Frederik Havgaard, who believes he knows who the killer is.

Louise locates Bjørn’s little sister Maria. Maria's caseworker suggests that Louise mentor the young woman, who is faced with the prospect of having her child taken away from her. Meanwhile, Bjørn is in hiding.

The police hunt for Bjørn is intensified. Following a search of Pelle’s home, Frederik and Louise uncover truths about Bjørn’s past, and a decision is reached on the forced removal of Maria’s child.

Another crime is committed. Frederik is convinced that Bjørn is the perpetrator, but Louise's investigations point to a different suspect. Bjørn turns to Louise and shares a secret with her that might close the case.

Three years on, Louise has moved to Aarhus to make a fresh start, but the past catches up with her when she meets Frederik again. He involves her in a new case in which a disabled woman has been found dead. Frederik thinks she was murdered, and the ensuing investigation seems to suggest that the dead body is a part of a larger pattern.

Louise and Frederik discover a connection between Bjørn and Alberte, who both grew up in the Breidablik commune. Louise visits the commune undercover in order to assist the police in their investigation and quickly notices the charismatic leader, Jon, who has a special relationship with Alberte.

Louise tries to get closer to Jon. Alberte becomes jealous and challenges Louise’s cover story. Meanwhile, Frederik discovers that one of Jon's old friends, who also owned Breidablik, perished in a mysterious fire.

Louise and Frederik put pressure on Jon to accept responsibility for his actions, but once again he takes advantage of his relationship with Alberte. Louise decides to confront the past.