After a deadly virus turns people into zombies, a small band of survivors seeks shelter in a snowbound town, convinced that the threat has vanished. Their relief is short-lived: they soon discover the infected have adapted to the harsh environment, making the danger far more insidious.
Two buses carry the last of the group's hope as they push toward a supposed safe zone. The first bus is ambushed by the infected, leaving the second bus - carrying the central figures, Jack, Patrick, Emma, and baby Lu - to improvise an escape. As they hide, Emma is bitten, altering the trajectory of everyone’s lives.
Nine years pass, and the story unfolds with quiet, stubborn resilience. Jack and Patrick live in adjacent houses separated by a fence, their truce strained to a fracture. Emma is gone, and Lu, now nine, remains under Jack’s care, whom she calls father. Patrick and Jack barely speak, and Lu is forbidden to leave the property, yet she finds companionship in the bond she forms with Patrick’s dog, tucked behind the barrier that divides them.
The fragile balance shatters when Patrick and his dog come upon a half-eaten fox. He trails the blood-wrought clue to an infected creature, tries to flee, and is momentarily blocked by a fallen tree. The beast looms, but its attention is drawn away by distant gunshots from Jack’s home. Patrick retreats to warn Jack, firing shots to signal danger, only to draw the herd toward them. The infected attack, and Patrick is bitten on the neck; a last, desperate act by the dog saves him when Jack falters at the moment of truth.
That night, Lu mourns the dog’s grave and slips out to lay flowers. She’s attacked by the infected, but Jack arrives just in time to pull her to safety. The encounter leaves him gravely wounded, and Patrick must intervene to save them. In the aftermath, they learn a startling truth: those who were infected near them did not turn harboring an unexpected immunity. They also discover that the infected have evolved—no longer relying on sight but instead wielding an acute and dangerous sense of hearing.
The next day brings a fragile spark of hope. Lu suggests inviting Patrick for dinner, and Jack agrees. Patrick starts to reach out through a radio contact, and a response hints at a larger human presence. It’s revealed that Patrick is Lu’s biological father; years earlier, he had fallen into alcoholism as Emma faced a violent attack and death, and Jack took Lu away. The three of them consider joining forces, and Patrick acquiesces to the plan. They trek to a warehouse to gather supplies, where a pregnant woman appears, claiming her group heard Patrick on the radio but their convoy was attacked. She reveals a chilling detail: the howling of the infected is how they call to one another.
They brace the house as the swarm closes in. The woman uses loud music to mask the infected’s hearing advantage, a desperate tactic that buys time. Yet the generator’s dwindling fuel threatens their acoustical defense. In a final, sacrificial bid, Patrick lures the horde away from the house, lighting a flare and shouting a defiant beacon as the monsters surge toward the fire. In a selfless act, he detonates the trap, drawing the infected away and enabling Jack, Lu, and the pregnant woman to escape toward a new dawn. They drive away, leaving the haunted town behind and watching the sun rise on a fragile, uncertain future.
