A disturbing challenge is issued. Michael finds a glimmer of hope for Freya, while Vincent's trust in Natalie is shattered.

Michael sacrifices everything for a possible future with Elsa. As his violent deeds catch up with him, Dan realises he will never leave Fortitude.

Dr Khatri attempts to cover her tracks when Michael presents the scientists with a miracle. Dan and Elena relive their trauma.

Michael finds something unexpected on the tundra, and Dan is confronted with what he is becoming, just as a heartbreaking discovery changes the town forever.

As the town attempts to come to terms with the recent tragedy, Petra and Ingrid seek the truth. Meanwhile, Dr Khatri moves a step closer to achieving her goal.

Natalie and Vincent head out into the wilderness and the police track down their suspect, but a dark turn of events leads them to question everything.

Michael hunts for the place he was held captive, and makes a shocking discovery. Annie Burgess arrives in Fortitude looking for answers.

In the remote Arctic town of Fortitude, two children make a remarkable find, while the discovery of a horrific crime brings a new arrival to the island that complicates Sheriff Dan Anderssen’s investigation.

Governor Odegard is presented with devastating news as Sheriff Dan struggles for his life, and a new threat makes its presence known.

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

Eric struggles to keep control as the body count increases. Meanwhile, Natalie and Vincent's field trip descends into chaos.

Dan faces his toughest battle yet as someone makes the ultimate sacrifice for the greater good, while Michael and Ingrid venture out in search of justice.

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.

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

The people of Fortitude take matters into their own hands. Dan seeks his own vengeance, but is there still a demon among the herd?

Oslo sends two new officers to attempt to make some sense of the anarchy in Fortitude. Dan Anderssen continues his descent into madness, bringing him face to face with a grief-stricken Michael Lennox.

A survivor of the deadly parasite makes a connection with Michael, but things take a violent turn. Dan continues to lose his grip on reality.

As the remote Arctic town struggles with government cuts and a missing sheriff, a chilling discovery proves that the horror isn't over for the locals.

The chilling thriller concludes with a dramatic and emotional finale. Vincent faces a life-threatening situation, while Dan must make a devastating decision.

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.

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.

In the penultimate episode, the truth about Billy Pettigrew is revealed. In the lab, Natalie and Vincent probe the cause of the disturbing events 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.

While Frank takes the law into his own hands, DCI Morton closes in on the truth about Pettigrew's death. Vincent and Natalie also make a discovery.