December 1942. Two young soldiers leave their posts at checkpoint 83 in North Värmland, Sweden and make their way through the ice cold winter night towards the Nazi-occupied Norwegian border. Sweden stands on the brink of invasion and they want to see the enemy everybody's talking about. But the adventure ends in disaster and soon thereafter Lieutenant Aron Stenström finds out that his brother Sven is one of the missing soldiers. With the odds stacked against him he is forced to go behind enemy lines on a secret rescue mission. Deep inside the Norwegian forests Aron realizes that a completely different kind of line must be crossed if they're to come out alive.

The unknown, large mafia organization is now showing its true face. The pressure that GSI and John Falk and his family have put on the organization, makes them fight back on all fronts. The rule book is thrown out. But to go after Johan Falk's family, to try to kill his wife, could be the biggest mistake the organization has done. GSI closes up around Johan's family, and the final battle begins.

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.