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.

In the middle of the summer holidays, the body of a drowned man with ligature marks on his wrists is recovered from Tammerkoski. The investigation by Koskinen's team is further strained by the death of a dubious music manager and the mysterious Carl Friedrich.

Another body is found in Lake Näsijärvi, and the link between the victims begins to unravel. As Koskinen ponders the cases, he sets sail with his son Antti, and his instincts prove correct, but at the same time he unwittingly puts Antti in grave danger.

Frightening events are happening in the Kaleva Chinese Wall neighbourhood that go far beyond the normal petty squabbles and complaints of neighbours. Koskinen initially finds it difficult to determine whether it is a case of a pathological stalker, or a quietly smouldering danger, until a house-hunter who has been terrorising his neighbours is found murdered in his apartment.

As the investigation at the Chinese Wall progresses, the pool of potential suspects slowly begins to shrink until there are only a few left. The tragic suicide of a young girl gives Koskinen the missing piece of the puzzle, and a surprising picture is laid bare.

As Luttinen's sick leave continues, Koskinen must attend the examinations herself. Under Koskinen's leadership, the police are on the trail of a long-running series of crimes in which lonely men have begun to die or disappear all over Finland.

The police's net around the criminals is tightening. They find themselves surrounded in a remote villa outside Tampere and refuse to surrender. A tragic shoot-out between the ruthless criminals and the police ensues.

Protesters against the man-made island in Tampere face a surprising amount of resistance, and a frozen body is found in the courtyard of Härmälä church. The activists appear to be involved in a homicide in one way or another, but Koskinen finds it hard to believe they are guilty.

The police get to the source of the money behind the scenes of the man-made island construction project. At the same time, Koskinen discovers the missing piece to a thirty-year-old investigation into a homicide that was thought to be an accident. The mayor's twin brother is also reported missing.

A headless corpse is found on Mannerheim's Rock, and the crime has ties to right-wing radicals. A possible eyewitness to the case is the petty criminal Aulis Autere, but he is unwilling to reveal his identity. The retired Roine takes an interest in Koskinen's investigation.

On the stairs of Tampere City Hall, a cut-off human head is found in a glass jar. An organisation called the Brotherhood of the Republic threatens to detonate five bombs in Pirkanmaa and a curfew is declared in Tampere. Roine tracks down the terrorist group.