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.

Alongside her partner Frederik Havgaard, new criminal profiling teacher Louise Bergstein takes the case of a gang member gunned down on his release from jail. Meanwhile, an ex-criminal is dragged back into his old ways.

Forensic evidence concludes that the same person killed Patrick and Pernille. As Louise and Frederik probe the link between the victims, an old gang-related double murder emerges, suggesting a potential quadruple killer.

In their search for Kim, a clue leads Louise and Frederik to Sweden. Meanwhile, Kim hides with his stepdaughter in a remote cottage. Louise and Frederik track Kim down, only to discover yet another devastating crime.

Under interrogation, Kim confesses to the old double murder and the killing of his girlfriend, but not to the murders of Patrick and Pernille. Dismantling Kim’s alibi, Louise has reason to come up with a new theory.

A revelation from Kim’s stepdaughter puts the spotlight on Kim’s old gangleader, Robin. Meanwhile, Kim is warned to keep silent, and an attack on Robin’s gang hints at an imminent gang war. Robin flees with his family.

Louise believes Robin was killed by the same murderer as the other victims, but Frederik suspects his death was a stand-alone gang murder. However, Louise convinces Frederik that a fatal car accident links the killings

With Louise's world falling apart, the case is taken over by Jacob, Frederik’s second-in-command. Jacob is determined to track down the killer, but must also contend with Louise - who soon discovers a shocking new lead.

Alongside Jacob, Louise tries to prove Gunnar’s guilt and uncover his motive. It appears that the loss of his daughter in a car accident and the driver's short sentence was the catalyst for Gunnar's murderous campaign.