Det er mandag morgen og Nanna har vært savnet siden halloweenfesten på skolen fredag kveld. Sarah Lund har sin siste arbeidsdag som etterforsker i Københavnpolitiet, før hun flytter til Sverige sammen med sin svenske kjæreste.

Sjefen hennes mener at etterfølgeren hennes ikke er klar til å gå rett på en så krevende sak som en forsvunnet tenåringsjente er og ber henne bli en uke til.

De finner Nanna, hun ligger død i bagasjerommet på en bil som er senket i ett tjern. Bilen tilhører valgkampanjen til kommunepolitikeren Troels Hartmanns som er midt inni en knallhard valgkamp.

Monday, November 3-Tuesday, November 4. Nanna's parents identify her body, and details of her sufferings are uncovered. Lund keeps postponing her departure, and tension arises between her and her new partner as they investigate the connection to city hall and a known criminal identified as the driver of the car Nanna was found in. Hartmann is faced with the choice of cooperating with the police or protecting his political future.

Wednesday, November 5-Thursday, November 6: The police investigate the crime scene they have found at Nanna's school and suspect her classmates Oliver and Jeppe of wrongdoing. Sarah Lund's fiancé shows up in Copenhagen, and she promises to leave for Sweden without delay. Meanwhile, Hartmann learns that a trusted employee has sent a suspicious email.

Thursday, November 6-Friday, November 7. Hartmann has won a new political ally, but is drawn into the murder case again when the police uncover new information which turns their suspicions towards teachers at Nanna's school. Theis Birk Larsen is troubled by the financial strain of the house he bought before Nanna's death. He begins to grow weary over the lack of progress in the case and seeks his own sources of information.

Friday, November 7-Saturday, November 8: Lund and Meyer investigate teacher Raman al Kemal's actions on the night of the murder. Hartmann learns of foul play at city hall, and his campaign is put under pressure when his opponent reveals Hartmann's ties with the suspect in a TV debate. On the day of Nanna's funeral, Lund is finally on her way to Sweden, and the appearance of one particular guest makes Nanna's father offer him a ride home.

Saturday, November 8-Sunday, November 9. Lund decides to stay in town to continue the investigation even though it puts her relationship with Bengt under strain. Rama is questioned as the main suspect. When Hartmann chooses not to suspend him, it puts his political position under threat.

Sunday, November 9-Monday, November 10. The police locate the place where Nanna was killed, and Rama is charged with the crime. Hartmann is fighting for his political life, but ends up making a tough choice. Meanwhile, Bengt is in a car accident on his way to Sweden, but tries to help Lund from his hospital bed. When the evidence is cast into doubt, Rama is released, but someone has other ideas.

Monday, November 10-Tuesday, November 11. Theis Birk Larsen's brutal punishment of Rama is interrupted by the police, and Theis is arrested. Lund and Meyer refocus their investigation on the car used by the murderer, knowing that if they do not make progress they might be taken off the case. As it becomes known that Rama is no longer a suspect, Hartmann shakes things up at city hall and relaunches his campaign.

Tuesday, November 11-Wednesday, November 12. Bengt leaves for Stockholm. Lund and Meyer are hindered in their investigation by a secretive boss, but Lund continues inquiries and is dismissed for her sins. Hartmann strikes a deal with higher powers in order to secure his bid for mayor, and a public debate is the scene of a change in political fortunes. Theis is released from prison, new secrets are uncovered about Nanna's last months, and in a last bid to forward the investigation, Lund unlocks the door to a new piece in the puzzle.

Sarah and Jan know who they are looking for but are puzzled by their superiors' reactions.

Sarah and Jan interrogate Troels, whose private information opens a new can of worms.

The spotlight of the police and media is now trained on Troels Hartmann, and he feels his political career is crumbling. Meanwhile strange things are going on at the town hall with fatal consequences.

Troels's political opponent Bremer wastes no time in taking advantage of his discomfort.

Sarah has walked into a life-threatening situation.

Sarah won't get on board when her superiors insist that Nanna's murder has been solved.

Lund and Meyer become convinced there is a link between Nanna's murder and a case that has remained unsolved for 15 years, and frantically try to find evidence. Meanwhile, Pernille and Theis are confused by the fact the case is far from closed, and Hartmann puts everything on the line in a bid to win the election.

Lund and Meyer get more than they bargained for when they visit an abandoned warehouse in their search for evidence. Meanwhile, a prime suspect disappears, and Hartmann struggles to get back into the political arena - but is contacted by a journalist whose efforts to dig up dirt have had some success. Theis and Pernille try to move on from the past 18 days' events and take their sons to see the new house.

Lund finds the odds stacked against her as the search for a missing suspect takes an unexpected turn, and Hartmann and Bremer take part in a dramatic, live TV debate amid a stream of revelations. Meanwhile, it seems something is amiss as Theis and Pernille prepare to move into their new house.

Lund is determined to catch Nanna's killer despite being taken off the case, and Hartmann is on a downward spiral - until he receives crucial information. Meanwhile, Pernille and Theis invite friends and family to Anton's birthday party - but there is a sinister twist to the evening in store.