After an accident, the musician and studied lawyer and criminologist Fredrika Bergman to the Stockholm police in the team for serious crimes. Together with her team leader Alex Recht and the policeman Peder Rydh, Fredrika is set on the first day for the case of a missing girl - which is not easy for the young woman. She finds comfort in her partner Spencer. When five-year-old Lilian disappears without a trace at Stockholm Central Station, everything points to an abduction. Fredrika and her colleagues Alex Recht and Peder Rydh work around the clock to find the girl alive. When the second child is kidnapped, everyone is aware: It is a serial offender. The team starts a race against time.

Tragedy strikes, another child goes missing and Fredrika, Alex and the others have a race against time to find the serial offender before any more children are harmed.

An elderly pastor couple is shot dead in his summer house. What initially looks like a double suicide proves to be murder. Fredrika Bergman and her colleagues Alex Recht and Peder Rydh determine in the summer house of the killed couple. The two daughters of the dead, Johanna and Karolina, could also be in danger. But who wants to harm the family? The Pastorenhepaar was active in helping refugees. Together with their two daughters, they led the aid organization "Aktion Freundschaft", which helps refugees to enter Sweden. The Stockholm Police Department believes that there is a radical right-wing group behind the crime. Then another body is found, and at the same time several shops are attacked. Fredrika Bergman and her colleagues are at a loss. How do the incidents fit together?

A priest and his wife, who work with refugees, are murdered in their home and a series of robberies is linked to the murders, but how and why? Meanwhile, Alex's marriage is in trouble.

Fredrika is very pregnant with her first child. The abduction of two Jewish boys is particularly close to her. In this case, the investigator reaches its limits. The two boys are found murdered a little later. They pulled a paper bag over their heads before placing their lifeless bodies in the snow. The incident recalls the story of "Paper Boy," an ancient fairy tale from Israel. "Paper Boy" wanders around at night, killing innocent children. A few days later, a young teacher is shot dead at a Jewish school. But it remains unclear how the killings fit together. Fredrika flies to Belgium to the grandparents of one of the boys to learn more about the tragic past of the family. However, only with moderate success. As the over-dedicated security chief of the Jewish school, Efraim, investigates on his own, the case for the investigator team becomes more and more opaque. And then the sister of one of the dead boys disappears: Can the team find Polly in time?

The body of the young Rebecca Trolle, who had been missing for three years, is found on a construction site in Stockholm. During the investigation, it turns out that the student was working on a sensitive topic for her exam: The murder that the well-known composer Thea Aldrin allegedly committed to her husband Niels decades ago. The police investigation found: Rebecca thought Thea Aldrin was innocent. Did anyone want to stop the young woman doing her research? Rebecca had old video footage from the then “Cinerama” club, which included Spencer Lagergren, Fredrika's partner and father of her daughter. The video shows a murder of a young woman. The clique is suspected and the police are also looking for Spencer - which puts Fredrika in a predicament.

Fredrika's private life is dragged into the investigation when Spencer is implicated. Meanwhile, Peder's brother sees more than he should and takes off, and developments in the case prove fatal.

Inexplicable murders occur: Richard Benke, who was suspected of murdering his wife six months ago but was then let go again, is found murdered. Efraim Kiel and a diplomat are also shot. The perpetrator apparently has inside knowledge of the police, because all victims were involved in murder cases. Alex and Fredrika suspect their colleague Torbjörn and search his house. But then the police officer is shot and seriously injured in the bureau's underground car park. Johanna, who was involved in the murder of her parents and sister, is also killed. The perpetrator apparently wants to ensure justice and order and leaves an inexorable blood trail.

Peder tries to get back on the investigation team as the body count mounts but he is not accepted any more. A dangerous killer is at large: could an insider be involved?