The isolated community of Fortitude in the Arctic Circle has never been the scene of a violent crime, so news of a murder rocks the residents. Sheriff Dan Anderssen investigates alongside newly arrived British detective Eugene Morton, while the killing is a disaster for Governor Hildur Odegard's plans to market Fortitude as an upmarket tourist destination.

As the chilling thriller continues, Sheriff Anderssen and the police close in on their murder suspect, while DCI Morton follows a different line of enquiry.

Dan and Frank go in search of a suspect; however, Dan's feelings for Elena are threatening to overwhelm him. Morton, meanwhile, uncovers a new piece of evidence.

Following Dan's loss of control, Morton takes over the murder investigation. Elsewhere, Elena's mysterious past is about to catch up with her

Shock waves reverberate around Fortitude as the killer is revealed, while Morton tunes his attention to the death of a scientist on the island months earlier.

While Morton uncovers new information about the death of Billy Pettigrew, Hildur makes a heart-breaking discovery. Another gruesome event occurs in Fortitude.

Panic sweeps through Fortitude as news of the second attack spreads. Dan and Morton must work together while Frank hopes the latest events will exonerate Liam

Frank takes the law into his own hands in a bid to clear Liam's name, while Morton realises Henry may have vital information about Pettigrew's death. A polar bear carcass arrives at the research centre's lab and as Vincent and Natalie analyse the corpse, they develop a theory about the recent events in Fortitude, which they feel compelled to share with Hildur and Dan

DCI Morton pursues Henry Tyson into the Arctic wilderness in search of the truth, while worrying test results force Governor Odegard to take drastic action

Dan races into the frozen wilderness to locate Henry and Morton, but he is forced to reveal the truth surrounding the death of scientist Billy Pettigrew. Back in Fortitude, Natalie has a disturbing encounter with Jason, whose behaviour is becoming increasingly bizarre, while her and Vincent's investigation leads to a particularly strange development in the inquiries into recent events.

Vincent's investigation leads him into a life-threatening situation, while Markus offers an alternative theory on what is plaguing Fortitude. Dan and Hildur launch a desperate hunt for Jason as the need to locate the mammoth carcass escalates and Eric and Yuri go head to head out in the wilderness. With events taking an unexpected turn in the Arctic community, Sheriff Anderssen must make a devastating decision.