On what is supposed to be detective Sarah Linden's last day of work in the homicide department, she gets a disturbing dispatch.

Theis and Pernille's worst fear comes to pass when their 19-year-old daughter is found abused and killed; Sarah postpones her move to Sweden to investigate.

Copenhagen detective Sarah Lund and her replacement-to-be Jan Meyer are on the trail of a principal murder suspect, but Jan's impulsiveness threatens to jeopardise the investigation. Meanwhile, important new clues turn up at the victim's school, while the campaign office of mayoral candidate Troels Hartmann is rocked by leaks of confidential information.

Sarah and Jan discover clues in the basement of the victim's school and the police pathologist has some shocking news for Sarah. Following the leaking of confidential information to the press, the atmosphere in Troels Hartmann's office is one of suspicion as his political career could be hanging in the balance.

Sarah realizes that Nanna's friend Lisa was involved in more events at the high school party than she had let on; Pernille deals with her grief in her own way, while Theis struggles to cope.

Troels heads for trouble after someone in his department tries to hide the fact that one of Nanna's teachers has a shady past involving a young student.