Monday, November 3rd. Police detective Sarah Lund is about to leave her job in Copenhagen to move to Sweden. Troels Hartmann is gaining ground in his efforts to lead his party to power at city hall. Theis and Pernille Birk Larsen are the happy parents of three children. The discovery of the blood-stained belongings of a young girl prompts a police investigation that will change the lives of all involved.

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) is faced with the choice of cooperating with the police or protecting his political future.

Lund and Meyer track down the driver, who ends up injured in the hospital, but also supplies an alibi. They refocus their investigation on Nanna's school. When the story of the connection to his campaign breaks, Hartmann finds himself in media turmoil. The Birk Larsens try to cope with their loss as they arrange the funeral.

The police investigate the crime scene they have found at Nanna's school and suspect her classmates Oliver and Jeppe of wrong-doing. Sarah Lund's fiance 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.

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.

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.