Johan Falk is with the wife of a dead mob boss down to Latvia to try to solve a mystery that has eluded him for three years. What Johan finds downstairs in a cottage outside Riga shocks not only himself but also the Gothenburg police special unit GSI 's new chief Sophie Nordh and the former chief Patrik Agrell. At the same time a Latvian mafia group is picking up hidden and forgotten Soviet military containers from the water-filled pits nearby. Containers filled with weapons. And everything is heading to Sweden! At the same time most of the original members of the Rydellgang are being released from a long prison sentence.