It is a few years after REYKJAVIK NIGHTS closed, Erlendur is now a detective working for the shadowy Marion Briem and is already divorced. It is 1979. A body of a man has been found in the blue lagoon, which has not yet become the tourist spot it is today. Apparently the victim fell from a great height and at first the police investigate the possibility that he has been thrown out of an airplane. As soon as they find out who he is - an engineer employed at the American base in Kaflavik - their focus shifts to the base and his work there, related to mysterious flights of classified planes between Greenland and Iceland. The authorities at the base are not willing to collaborate, in fact they do everything in their power to hinder the Icelandic police. Fully aware of the danger they are running, Erlendur and Marion continue investigating with the help of an officer from the base. In parallel, Erlendur is asked to investigate the cold case of a young girl vanished into thin air on her way to school forty years earlier.