Sarah and Jan's boss decides that Nanna's case is solved, the murderer being Jens Holck, but Sarah isn't sure and continues her investigation alone. At the town hall, Bremer is seeking a truce, but Troels apparently has something to unveil. While Sarah's private life is falling apart, Pernille and Theis try to reconcile their differences.

Sarah and Jan are convinced that there is a link between Nanna's murder and a 15-year-old unsolved case. Furthermore, they think they know where to find the evidence and the perpetrator - but it's a race against time. Pernille and Theis see Nanna's last greeting and are puzzled by many things. Troels Hartmann is counting on winning the election and is willing to put everything on the line in regard to Bremer and the public.

When Sarah and Jan go to check out an abandoned warehouse to look for evidence, they're not alone - and it has dire consequences. At the same time, a taxi driver has vanished from the face of the earth. Troels is struggling to get back into the political arena, but is contacted by a journalist who seems to be rather well informed about what has been going on at the town hall. Moreover, interesting information is revealed about Rie. Theis and Pernille are trying to move on and take their children to see the new house, but there is also evidence of the crime to be found there.

The police hunt for the taxi driver who has disappeared takes a new turn. Meanwhile, Sarah is overwhelmed by problems in every aspect of her life. Troels and Bremer battle it out in a live TV debate, of which the outcome is unexpected and vehement. At the town hall, Troels is confused about what's going on. Theis and Pernille are preparing to move into their new house, but something's wrong.

Sarah has been taken off the Nanna Birk Larsen case, but continues her investigation. She is sure of the identity of the perpetrator, but lacks the incriminating evidence. At the town hall, Troels brings himself down like a brick, but then Bremer sends for him because he has important information. Pernille and Theis have a birthday party for Anton, and an eventful night ensues.

Now in a routine job in the country, Sarah Lund is contacted, when police headquarters in Copenhagen is stuck in a complicated case, where a woman lawyer has been found battered and killed. In the government building newly appointed Secretary of Justice Thomas Buch chairs some intricate political negotiations - while soldier Jens Peter Raben awaits conditional release from the criminal psychiatric ward. The three individuals do not know each other - but suddenly they have something in common.

The police now have two murder cases, both victims with military backgrounds. Important leads indicate a connection between the two, so Sarah Lund and Ulrik Strange must try to enter several secretive circles. In Parliament, while in the middle of complicated political negotiations, Buch deals with the publicised terror threat and a possible connection to resident Islamists. At Herstedvester Prison, Jens Peter Raben is still in isolation when he finds out that his friend has been found murdered.

Jens Peter Raben has escaped from Herstedvester Prison, and meanwhile something in his statement to the police doesn't ring true. When residents Islamists are arrested, Lund and Strange disagree on what leads to follow, and Lund gets her way despite Brix' order to the contrary. Meanwhile, Buch is swamped with problems in Parliament when the Opposition learns of an as yet undisclosed memorandum regarding the first murder. Raben needs assistance and seeks out an old friend from Team AEgir, and shortly after he runs into another member of the team.

Raben and a friend from Team Aegir are to meet, but he arrives too late. The police discover yet another murder victim, and everything indicates that it's the same perpetrator as in the previous crimes. However, Special Branch is no longer convinced that the police are on to the right suspect. Thomas Buch is under pressure from the Opposition and the Prime Minister in the on-going negotiations, and he learns something very surprising about his predecessor.

Sarah Lund and Strange are in Sweden to question and protect the only survivor of the group apart from Raben. She flees when she discovers that explosives have been planted in her house. Buch causes trouble in front of reporters in Parliament, much to the displeasure of the Prime Minister, the Minister of Defense and his supporting party. Then Buch resorts to unconventional means. The top police management and Special Branch interfere in the investigation, and meanwhile Lund sees the case from a new angle.

Sarah Lund is convinced that the body of the fallen soldier, Per K. Moller, is not the one in the buried coffin, but she needs to be certain. Jens Peter Raben is now the sole survivor of his group, and he realizes that Preacher has lied about his knowledge of Anne Dragsholm. Buch's fellow ministers have run out of patience with his insufficient efforts in the current situation including the terror threat, while Buch wants to know more about what his predecessor, Monberg, was up to. And things come to a head at police headquarters.

Denmark is the midst of a election race, set against the backdrop of the financial crisis. With ten days to go to the election, Detective Chief Inspector Lund prepares to celebrate her 25th year in the police force and looks forward to the prospect of a new job in the force. However, her relative peace is shattered when body parts are found at a Copenhagen dock only hours before a scheduled visit by the prime minister.