In the grim Alaskan winter, a naturalist hunts for wolves blamed for killing a local boy, but he soon finds himself swept into a chilling mystery.
Medora’s husband, Vernon Slone (Alexander Skarsgård), is overseas in Iraq, where he is shown mercilessly and efficiently gunning down Iraqi militants. While stationed at a checkpoint, Vernon wanders off and comes across an American soldier raping a local woman. Vernon stabs the soldier and leaves the woman with his knife to finish him off. Moments later, shooting breaks out at the checkpoint: Vernon is shot but survives to be sent home.
In the morning, Core leaves town to track the wolves and meets an old native woman, Illanaq, who tells him he is going the wrong way, and that Medora ‘knows evil’. Core tracks the wolves, coming across the hot springs Medora mentioned, and spots a pack of wolves eating their young. Unwilling to shoot them, Core returns to Keelut. At the Slone house, he finds Medora missing, and the cellar door unlocked. Downstairs, Core finds Bailey’s frozen, strangled body, and calls for help. The police investigate, and the native villagers claim Medora is possessed by a wolf-demon called a tournaq.
Vernon’s old friend and father to another missing child, Cheeon (Julian Black Antelope), meets him at the airport and drives him to meet with police chief Donald Marium (James Badge Dale), Core, and several other officers at the morgue. After Core and Marium leave, Vernon shoots the remaining officers and the coroner. Vernon and Cheeon then take Bailey’s body and bury it in a pine box, marking it with symbols in their blood. Vernon then returns to Keelut and kills Illanaq.
Core, remembering the woman’s prescient warning, and the police, following up on the murdered officers, arrive in Keelut at the same time. Marium and a few dozen officers take up positions outside Cheeon’s house as the chief approaches to ask about his involvement with the murders. Cheeon, who refuses to come quietly, later opens up barn doors on the upper level of his house, and fires on the clustered police with an M60 machine gun, killing many. Marium flanks the building and shoots Cheeon from the inside.
At an inn outside a tourist mine where Medora was sighted, Vernon meets John, an elderly hunter, who treated Vernon as a child for his seeming psychopathy with wolf-oil. The hunter invites Vernon to take a mask, saying he “needs to let the wolf out a little.” Vernon chooses a mask from the wall, puts it on and kills John. As he leaves, Vernon is shot in the shoulder by the innkeeper, leading him to visit an old friend, Shan, who pulls the bullet from his shoulder.
Core and Marium theorize that Medora killed Bailey to save him from darkness. Core recalls Medora’s saying the nearby hot springs are “a good place to get clean” and thinks she might have gone there. They agree to go after Medora and try to catch her before Vernon does.
Vernon, meanwhile, has a dream of himself and Medora in the hot springs. Now awake, he overhears Shan’s informing the police of his presence. Vernon puts on the mask and stabs Shan in the head. The police force splits up, half going to the crime scene at Shan’s house, and Marium and Core going to the hot springs.
While looking at some wolf tracks in the snow, Marium is shot through the neck by an arrow fired by Vernon, who is wearing the mask. Core leaves Marium’s body and heads to the hot springs, hoping to intercept Vernon. He finds Medora there, and is then arrowed in the chest by Vernon.
As Vernon strangles her, Medora pushes the mask off his face. He releases her and they embrace. Core falls unconscious.
After Core wakes, Vernon removes the arrow from Core’s body before leaving with Medora. Core crawls outside the cave, encountering a pack of wolves. He is found by a father and son with a snowmobile and brought to their home for care, as Vernon’s mother looks on. Vernon is seen digging up Bailey’s grave with Medora; they pull the coffin along with them as they trek through the snow. Core wakes up in hospital, his daughter Amy at his bedside.