The body of a murdered programmer is found in the control centre of the Tampere tramway. The people in the department seem to have all sorts of secrets, and one seems particularly guilty. But Koskinen thinks his guilt is all too obvious.

Malware has disrupted the Tampere tram control centre and darkened Tampere. Koskinen persuades the head of the crime unit to allow Roine, who is on sick leave and working in the archives, to join the investigation. The duo track down the real "Scavenger" and Koskinen is faced with a fateful choice.

In Hervanta, the Tampere police's nightmare comes true: a 16-year-old girl is found strangled with fishing line in a forest. It seems that a mentally ill murderer is on the loose, but the police have no idea who he is. The father of the murdered girl goes into a vengeful rage and launches his own investigation.

The Fishing Line Strangler has struck again. Koskinen and his team race against time to find the killer as the number of victims grows. A former colleague, Roine, who has ended up in a psychiatric hospital, provides a crucial clue. Will Koskinen have time to act before an innocent man is murdered in revenge?

Koskinen has been promoted to inspector and the challenges of a senior position begin when a jewellery store robbery ends in a sudden shooting. Why did the robber shoot a bystander, a complete stranger?

The trail of blood draws Koskinen from the office to the field to investigate a robbery that has turned into a homicide investigation. Koskinen's good friend and colleague Roine is in a psychiatric hospital. When patients start dying of strange heart attacks, the old detective's suspicions are raised. But can Koskinen take his sick friend's suspicions seriously?

The body of an unidentified man is found in a ditch. It turns out that the victim had no chance to escape his killer. The investigation leads to a shelter called Hukantupa. The team is also investigating a series of pharmacy robberies, in which the perpetrator is trying to escape from the grip of the police with increasing recklessness.

In Hukantupa, a gang of eccentric, disabled men vent their hatred and bitterness of their fate in a rowdy drunken brawl. Koskinen's team of investigators are faced with a terrifying puzzle: are the inhabitants of the house haunted by a mad murderer who believes he can save them from their fate, or is it the resentment from within the house? Surprisingly, a series of pharmacy robberies are also linked to the events at the Hukantupa shelter.

An old man is brutally assaulted in Nekala, Tampere, and an arson attack takes place in Hervanta. The perpetrators are suspected to be a gang, the youngest member of which is a 15-year-old girl. Soon one of the gang members is found murdered.

Koskinen and his team of investigators are tasked with solving a seemingly absurd series of crimes. The task is not the easiest, and the young people caught up in the maelstrom of events are also in distress, dying one by one. Will the young people be driven by guilt or fear? Dark secrets are revealed behind the murders of the drug-addicted youths, and in the end, Koskinen and his colleagues are no longer safe.