The series "Jakten på en mördare" tells the story of the investigation into the brutal murder of a ten-year-old girl named Helen Nilsson. The tragedy occurred in the late 80s in a small Swedish town called Herby. The police were unable to make any progress in the investigation for several decades - from 1989 to 2004. At first, many townspeople hoped to find the little girl alive. The search for the child was carried out by Helen's relatives, law enforcement officers, and a large number of activists. But the revelation became a shock for the entire country.