Fortitude is a place like nowhere else. Although surrounded by the savage beauty of the Arctic landscape, Fortitude is one of the safest towns on earth. There has never been a violent crime here. Until now. In such a close-knit community a murder touches everyone and the unsettling, mysterious horror of this crime threatens the future of the town itself.
The local Chief of Police, Sheriff Dan Anderssen (Dormer), has to investigate alongside DCI Morton (Tucci), the detective who has flown into Fortitude so fast that questions are being asked about how much he knew, and when. As these two cops try to make sense of the killing, each finds compelling reasons to mistrust and suspect the other.
The murder is a catastrophe for Hildur Odegard (Grabol), the town's Governor. It threatens her ambitious plans to transform Fortitude from a mining town into a site for high-end tourism. And for Henry Tyson (Gambon), a wildlife photographer who only has weeks left to live, the murder is the catalyst to unearthing Fortitude's darkest secret.
Also key to the story are Charlie Stoddart (Eccleston), an English scientist who heads up the Arctic Biology department at the Fortitude Arctic Research Centre, talented young scientist Vincent Rattrey (Treadaway), the newest member of Stoddart's team, and Jules Sutter (Raine), who is married to Frank Sutter (Pinnock), Fortitude's chief search and rescue pilot.
As the cold Arctic darkness gives way to endless summer nights, this apparently idyllic community struggles to make sense of the murderous horror that has been let loose in its heart.