The body of a drowned man is dragged up from the Tammerkoski rapids. Although the man was found in Lake Näsijärvi, he was not drowned in lake water but well water, and the marks found on his wrists are determined to be caused by a rope.
Koskinen and his son are sailing near the area where the first body was found and Koskinen gets an idea and goes to investigate a nearby cluster of islands. Koskinen unwittingly puts Antti in great danger.
An uninvited guest visits people's flats and leaves behind threatening messages. A resident who has been stalking and terrorizing his neighbours is found killed in his flat. Almost every resident in the house has a motive.
As the investigation progresses, only a few suspects remain. A young girl's tragic suicide in another part of the city indirectly provides Koskinen with the missing piece of the puzzle.
A bachelor living a quiet life has been stabbed in his flat and he swears he did not know the attacker. Koskinen gets on the trail of crimes that have been committed all over Finland in which lonely men have died or gone missing.
The perpetrators turn out to be two women swindling money from lonely men. The women are not only driven by a lust for money but also their desire to take revenge on their victims for the humiliations they suffered in their previous lives.
Environmentalist opposing to an artificial lake that's being planned in Lake Näsijärvi demonstrate against the project and go on hunger strike. The demonstrators are attacked violently.
Koskinen finds out the spiral of violence related to the case began years ago. The Mayor's twin brother has gone missing. The case gets a horrifying twist when a severed finger is found between the pages of the Constitution of Finland.
The finger found in the library belongs to the mayor's brother. A headless body is found at the foot of the Mannerheim monument. The police receive a threat about five bombs having been armed around Tampere.
The retired Roine gets interested in the case, finds the group behind the acts and gets captured by them. The group intends to execute the mayor of Tampere at the town hall square and live stream their declaration of war online.