A Spanish-Finnish couple is found murdered in cold blood in the Oulu region. Hilkka Mäntymäki and the "new sheriff in town" Jami Kalliola start investigating the case.

Hilkka Mäntymäki's team is strengthened by the arrival of Luisa Salinas, flown in from Spain. The investigation leads the police on the trail of a transport company specialising in the waste business.

Hilkka, Luisa and Andrés arrive in Gran Canaria to raid a container that has left Finland. Jami Kalliola continues to investigate the case in Finland. The murders reveal a link to a professionally run smuggling business.

The killer leaves more bodies in their wake. Hilkka and Luisa find barrels full of radioactive mining waste in a storage area abandoned by the army. Andrés meets a man from his past in prison.

Hilkka tracks down the killer and the forces behind the smuggling plot are revealed. An internal threat endangers the life of a witness and the entire investigation - will Andrés and Luisa get there in time?