Salmander and Johanne sneak into Hellfish at night and come across something strange. They overhear Bosse Nova talking about the infamous serpent Tulla, and despite Salmander's chronic seasickness he decides to defy his fear and look into this phenomenon.

Policeman Salmander loses his job in Oslo and must spend dismissal time in Hellfjord, a shit hole of a place far north in the country. As soon as he arrives, strange things start to happen in Hellfjord, and the seemingly quiet place turns out to conceal dark secrets.

The transferred policeman Salmander just found a dead body on the island and quickly becomes convinced that there is talk of a murder. There are several suspicious people in the community, but as an alien and southerner he gets little help from the locals.

After breaking out of Solvik jail in a spectacular way, Salmander finds himself in a even more difficult situation. The local journalist Johanne comes to the rescue just before it goes seriously wrong, and together they connect the dots that finally lead to Bosse Nova, owner of a local fishery.

Salmander's notice period is over and he is sent back to Oslo. He continues to investigate the murder mystery as a civilian. Meanwhile in Hellfjord, Johanne finally gets to the bottom of Bosse Nova's hidden activities by herself, and reveals a conspiracy that is bigger than they ever could have imagined.

Salmander goes undercover in Solvik jail to follow a lead in the murder case. When his only ally in prison dies from a peanut-related accident, Salmander is put behind bars for real. Not only must he follow a trail in the case, he must also find a way to get out of prison. Meanwhile, Johanne finds a very special clue in Hellfjord's murder mystery.

Salmander and Johanne have each on their own exposed Bosse Nova's drug business. Without police help, but armed with confidence and a machine gun, Salmander comes back to Hellfjord for a final showdown with Bosse in the fish factory Hellfish.