While recovering from a severe injury, Wisting receives an anonymous letter in the mail. The cryptic content leads Wisting to suspect a possible injustice in an old murder case where a 17-year-old girl was killed, and her ex-boyfriend was convicted.

A new anonymous letter leads to fresh evidence, but not everyone is happy to see the old murder case back in the spotlight. Wisting realizes he is being opposed by powerful forces within the police, as he keeps searching for the secret messenger.

A breakthrough in the case takes Wisting to Vilnius for a meeting with Interpol investigator Harriet Dunn. What is meant to be a simple questioning of a suspect becomes far more complex for both of them - both professionally and personally.

New DNA evidence appears to solve the murder of Tone, but Wisting still feels that something is amiss. Wisting and his colleagues must call on all of their skills and experience to avoid a dramatic and dangerous situation.

Just as Wisting is hailed as a hero, he faces accusations of evidence tampering in a previous murder case, leading to Vidar Haglund's potentially wrongful conviction. Line tries to keep her father out of the headlines, by chasing a news story on a recent murder.

An internal investigation of Wisting begins after his suspension. Torunn leads the investigation about a missing woman. Line runs into an ex when she works on her Ravneberg article.

Lines and Wistings investigations are linked, and the search for the serial killer becomes increasingly intense. At the same time, Wisting's worst nightmare becomes reality.

When a corpse appears in the net of a local poacher, the two killings are linked. Line suspects that Wisting has had a relationship with the manager at the care center.

Six-year-old Clifford Greenwood vanishes from the family hotel Wildenvey and an employee is found dead. Detective William Wisting believes the boy was kidnapped. The Greenwood family is shocked, but Wisting discovers they have secrets.

Wisting tries to save his reputation by conducting his own secret investigation into the Cecilia case. Torunn believes that Linnea is behind her own disappearance, but her parents are convinced that she is in danger.

Wisting takes desperate methods to show his innocence, while the internal investigation looks more closely at his entire department. Benjamin examines who can lie behind Linnea's disappearance.

Wisting and his team are warned about a cruel crime scene in Larvik. The severed head of a young asylum seeker is found on a stake in the middle of the square. FBI agent Maggie Griffin returns to assist in the case.

Investigator William Wisting makes a frightening discovery: A corpse has been found among the spruce trees in a Norwegian Christmas tree field, and turns out to have links to a sought after American serial killer.

With the help of FBI agents Maggie and John, Wisting tracks serial killer Robert Godwin to a remote farm, but do they keep the mission secret from the press before Godwin runs?

Wisting and the FBI suspect that Godwin may be behind twelve cases of missing persons in Norway. Vidar Haglund is released from prison, and Line questions the circumstances surrounding Viggo's death.

Wisting takes the help of a former colleague to solve Cecilia's murder, and to figure out who fiddled with the evidence. Line finds a video that links the charges against Wisting to Linnea's kidnapping.

William Wisting and his team are hit hard when a crime scene inspection with serial killer Tom Kerr goes horribly wrong. Wisting's daughter Line now has to deal with the consequences of her documentary causing it all.

Wisting tries to gather the team after the tragedy that has befallen them. He is forced to cooperate with Kripos investigator Stiller in the hunt for the mysterious helper.

Maggie is forced to share information, which she has previously kept secret from Wisting. The investigation takes a whole new turn, and leads Wisting and Maggie on a new hunt across the border into Sweden.

In Sweden, Wisting and Maggie find a former victim. Together with the Swedish police, they are drawn into a fierce police action, and the final settlement is both intense and surprising.

Clifford's family receives a ransom demand and a cryptic message. The clues suggest Clifford has been taken as a revenge against his grandfather. Wisting's daughter, Line discovers her ex, Tommy, has fallen into very bad company.

Wisting is under pressure, still without leads. Clifford's parents await contact from the kidnapper but receive a mysterious message that leads them to a gruesome discovery. It's clear the kidnapper wants to tell them something, but what?

Line's obsession with Viggo's death leads to a quarrel with her father. Wisting and the FBI find more of Godwin's victims, and the FBI agent John makes a mistake that has serious consequences.

A new disappearance makes Wisting and Stiller fear that the killers are about to flee the country. But has the new victim really been kidnapped? A new clue causes the police to arrest a suspect.

Line's shocking findings overturn the police's theory of "The Other". The perpetrator gets rid of loose threads and time is running out. Wisting discovers the secret that his daughter has kept hidden from him.