A Finnish family is found murdered in cold blood in the Costa del Sol, Spain. The crime investigator Hilkka Mäntymäki (Riitta Havukainen) is sent to investigate the homicide that has shocked the peaceful Finnish community in Fuengirola.
Hilkka is sorely missed at home. But Andrés (Fran Perea) badly needs her help in solving the case. Gradually the crime investigators start unravelling the events that have led to the tragic death of the Saitama family.
The surprising links between the deaths of two Finnish women start ringing the alarm bells in Andrés and Hilkka, who is now back in Finland. Soon it appears that there might be a third victim connected to the case.
The killer strikes again. Hilkka returns to Spain. Andrés starts suspecting that Police Chief Coréa (Oscar Zafra) is protecting someone. Hilkka and Andrés's friendship gets deeper after a night spent on the beach.
Hilkka, Andrés and Luisa (Maria Roméro) find a new suspect. In a nursing home Aarne (Risto Tuorila) ponders what happens to people after death. But who is the mysterious JK and what is their connection to the estate agent Maikki Mattson.
Hilkka is kidnapped. Hilkka's captor tells her a sad story from the distant past, about a youth camp called The children of summer. The tale leads Hilkka towards a time and a place where the evil came into being.
All the police forces in the Costa del Sol have been alerted to find the murder suspect. The chase culminates in a gunshot in front of the police station, and the consequences are fateful.
Hilkka and Luisa track the murderer, while Andrés is moved aside from the investigation. Aarne has found his way up north, to his favourite fishing grounds. Darkness is inevitably falling, both in Spain and in Finland.
