In 2004, an eight-year-old boy and a 56-year-old woman are stabbed to death in broad daylight in the Swedish city of
Linköping. In spite of spending more than 15 years on the case, making it the largest criminal investigation in Swedish history (except for the one after the
assassination of Olof Palme in 1986), the police can't find the murderer and the lead investigator is told to close down the investigation. But then he happens to read an article about a 40 year old murder case in the United States having just been solved through a brand new method, where a murderer's DNA is used to find ancestors on genealogy websites and then follow their family trees back to modern times. The investigator asks his bosses to let him try this as a last attempt before making it a
cold case. They agree, so he engages a genealogist who specialises in finding people's recent relatives by employing this method, and together they manage to find the murderer. ==Cast==