Following a shocking attack on a politician in Reykjavik, Chief of Police Andri makes a return to his rural hometown, a place where the dark events of the past still haunt him.

Andri and Hinrika suspect that two young local farmers, Torfi and Skuli, are implicated in Finnur’s murder.

Torfi and Skuli remain the best lead for the attack the chief of police is investigating. And Skuli is still on the loose.

The police have foiled a terrorist plot but they’re left no closer to having solved the mystery of who killed Finnur, or why Gisli took the actions he did.

Ketill finds dead animals up by the lake and has his suspicions about why Skuli became so ill hiding out in the mountains. Meanwhile, Ebo is beginning to feel in danger.

In the aftermath of another killing at the plant, Vikingur is found covered in blood, and with his fingerprints on the murder weapon.

The polluted lake has been discovered and the town's water supply has been turned off to prevent further cases of sickness. Andri and Hinrika are chasing up leads all over town.

Now that Thorhildur has given the police the lead they need, Andri must get her out of town before the killer finds out what has happened.

The true identity of the killer is revealed and Andri and Hinrika face a race against the clock to protect the people they love.