Ten days after lawyer Anne Dragsholm was found dead at a WWII memorial, the police have her husband in custody for her murder. But the chief of investigation calls on Sarah Lund, who has transferred away from the crime squad, to return to Copenhagen to look over the case. Meanwhile, a young politician is made minister of justice after his predecessor is incapacitated, and a convict seeks parole from a detention facility to be with his wife and child

Sarah Lund officially joins the investigation into the murders of Anne Dragsholm and soldier Allan Myg Poulsen, who was found butchered in a warehouse. A published video of the captive Dragsholm suggests the assassinations are acts of terrorism, and the police look into links with Islamic extremists. At Parliament the case puts new minister Buch's terrorism legislation in jeopardy when the government's right-wing partners demand a tighter grip on extremism. Prisoner Jens Peter Raben takes matters into his own hands after being denied parole.

While intelligence services insist that the investigation should focus on possible terrorism links, Raben's escape strengthens Lund's interest in his links with the victims. Raben himself seeks information from other old army buddies. Buch is hit by the revelation of a secret memo about the Dragsholm murder, and the actions of the former minister come into question.

The murder of another former soldier, David Grüner, prompts inquiries into his and Raben's army squad and a particular event during the group's Afghanistan mission a few years before. Lund and Strange track down one of the remaining members in a remote Swedish island. Buch is under pressure from above to cave to the right wing's demands about banning Islamic organisations, but new information about former minister Monberg's relationship with one of the victims makes him weary of acting too hastily.

The police investigation comes under fire after soldier Lisbeth Thomsen was killed by a bomb planted in her boat, but Brix keeps Lund and Strange on the case. They try to learn the truth about the Afghanistan mission and pay a visit to the mother of a fallen soldier who may be connected to the case. Buch causes scandal when he interrupts his own press conference, and the prime minister wants him to come up with answers. Raben remains on the run, but seeks help from his former comrade the chaplain.

Lund demands that the grave of the dead soldier Per K. Møller be dug up, but her theory that the coffin is empty is proven wrong. She is suspended from the investigation and takes time to attend her mother's wedding until developments bring her back into action. Buch brings his assistant Karina Munk back after she resigned, despite permanent secretary Plough's objections. They pay a visit to former minister Monberg, who has gained consciousness at the hospital, to find out what he knows about the ongoing case.

After finding the chaplain assaulted in his church Sarah Lund chases the offender, but ends up battered in an alley. She is brought back in charge of the investigation. Monberg has taken his own life shortly after his confrontation with Buch. Buch comes about a previously unknown medical report and decides to challenge his colleague the minister of defense over his secrecy. Raben continues his rogue investigation and tracks down a former soldier who he believes to be responsible for the Afghanistan incident.

Jens Peter Raben has been shot by Strange during an escalated situation where Raben seemed to recognize Strange. Raben survives, and Lund finally has the chance to interrogate him. She finds herself investigating her partner's past in the military, but also uncovers a soldier's video diary that leads to a new suspect. At the barracks Colonel Jarnvig begins to consider the possibility that Raben's version of events in Afghanistan might be true. And after a week in the job Buch faces forced resignation, but finds help from an unexpected source.

Thomas Buch has refused to resign and calls a party meeting to challenge the authority of the prime minister. He finds an unexpected ally in the minister of defense. Lund and Strange head to Afghanistan to seek out Frederik Holst, a doctor with a grudge against Raben and his squad. They also decide to visit the house where a family was allegedly killed while the Danish soldiers were there. Back in Copenhagen, Brix organizes a search of the army barracks and finds a locker full of incriminating objects.

Lund and Strange return from Afghanistan with their findings, though Brix has become convinced of the guilt of officer Bilal, who has run away with Louise Raben as his hostage. Buch has been held overnight by the police, but returns determined to bring down the government he is part of. Secrets are uncovered at the ministry and in the military, revealing a conspiracy to conceal vital information. Lund puts together some pieces of her own, and it comes to a lethal confrontation with the killer.

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

Following the kidnapping of Robert Zeuthen's daughter Emilie, Copenhagen Police put every effort into tracking down the perpetrator and finding the little girl. Meanwhile, the kidnapping has quickly become a hot potato in the election campaign and Prime Minister Kamper must deal with the fallout.

Following the dramatic murder of public prosecutor Peter Schultz, it becomes clear that Emilie Zeuthen's kidnapper will stop at nothing to recover his debt. However, police remain clueless about the perpetrator's motives. Lund and Mathias Borch try to cooperate on the case, while Lund makes a surprise reconciliatory visit to her son Mark. The prime minister's team try to limit his public involvement in the affair of the kidnapping, but yet more troubling information emerges which will make it difficult to focus on the election campaign.

Another failed attempt to capture their man leaves Borch and Lund with a dilemma - should they obey the perpetrator's instructions or take action in spite of his directives, thereby risking Emilie's life? Further links to an old unresolved police case continue to emerge, shedding new light on the investigation while marring the prime minister's political life.

The kidnapper continues to insist that he's seeking to recover a debt. If Lund is to save Emilie's life, it will be up to her to find out what the debt is and how it should be repaid. Following a request for Robert Zeuthen's life in exchange for Emile's, police set out to organise the exchange. Meanwhile, the integrity of a few high-ranking politicians is called into question, as Prime Minister Kamper takes a dramatic decision.

Police are led to the Jutland region by their investigation. Here, Borch and Lund make an eerie discovery and find themselves in danger. Back at HQ, pressure grows on Brix, as management question his judgment. Prime Minister Kamper hesitates in implementing his decision following doubts about Emilie's fate. Ussing is found to have been harbouring a secret.

A new element turns out to play a role of great significance in the investigation. Borch and Lund have a hard time shaking off their Jutland experience, and their working relationship suffers as a result. Robert and Maja harbour hopes that Emilie may still be alive and Zeeland throw all their resources into tracking her down, as a secret is revealed from an unlikely source within the family. Police run checks on Ussing's movements over the last couple of years.

A suspect is taken in for examination as the police try to find out more about the notebook they discovered, but things go less than smoothly. The prime minister and his close aids become the focus of police attention, as Karen is also found to be hiding a dangerous secret which could prove fatal for the government. Borch and Lund's trip to Jutland begins to have consequences. Robert Zeuthen intensifies the hunt for his daughter, despite coming under heavy pressure from the Zeeland board. Maja takes sides. A witness turns up who may have important information about Emilie.

Sarah Lund is held back in her attempts to make headway with the investigation, but at least the perpetrator finally has a face. Will he lead police and the Zeuthens to Emilie? Prime Minister Kamper is trying to clean up his circle as he attempts to find out what happened to his son. Suspicions arise about a trusted Zeeland figure as Robert Zeuthen considers drastic action.

It's election day and the Prime Minister has everything to gain, as long as Emilie's fate remains uncertain. Kamper is still haunted by personal demons, and issues of loyalty from within his own ranks rear their ugly heads once again. Meanwhile, as Lund and Borch start to look ahead, police are led to an undisclosed location in a last ditch attempt to find Emilie before it's too late. They are followed by a now dangerously tense Robert Zeuthen. Will the operation succeed in bringing the girl to safety?