The police find out about the crime the way everyone does: on Snapchat. The video shows a terrified young woman begging for forgiveness. When her body is found, it is marked with a number “2”. Detective Huldar joins the investigation, bringing child psychologist Freyja on board to help question the murdered teenager's friends. Soon, they uncover that Stella was far from the angel people claim, but who could have hated her enough to kill? Then another teenager goes missing, more clips are sent to social media, and the body with a “3” is found. Freyja and Huldar can agree on two things at least: the truth is far from simple. The killer is not done yet. And is there an undiscovered body carrying the number “1” out there?

Vaka sits on the cold steps of her new school. Her father appears to have forgotten to pick her up, her mother has forgotten to give her this week’s pocket money, and the school is already locked for the day. With no way to call home, she resigns herself to waiting on the steps until her father remembers her. When a girl approaches, Vaka recognizes her immediately from class, and from her unusual appearance: two of her fingers are missing. The girl lives at the back of the school, and Vaka asks to call her father from the girl's house. That afternoon is the last time anyone sees Vaka. Detective Huldar and child psychologist Freyja are called in and soon find themselves at the heart of another shocking case.

The only person who might have the answers to a baffling murder case is the victim’s seven-year-old daughter, found hiding in the room where her mother died. And she’s not talking. Newly promoted, out of his depth, detective Huldar turns to Freyja, a psychologist, for her expertise with traumatized young people. Freyja, who distrusts the police in general and Huldar in particular, isn’t best pleased. But she’s determined to keep little Margret safe. It may prove tricky. The killer is leaving them strange clues, but can they crack the code? And if they do, will they be next?

Aldis hates her job working in a juvenile detention center in rural Iceland. The boys are difficult, the owners are unpleasant, and there are mysterious noises at night. And then two of the boys go astray. Decades later, single father Odinn is looking into alleged abuse at the center. The more he finds out, though, the more it seems the odd events of the 1970s are linked to the accident that killed his ex-wife. Was her death something more sinister?