After a virus turns people into zombies, a small group of survivors seek refuge in a snow-covered town, believing the virus and all of its monstrous creations had died out. But they only discover the infected had adapted to the environment change, for worse.
Some remaining survivors on two buses are trying to make it to a safe zone. The first bus is attacked by the infected. The people in the second bus, including the main characters (Jack, Patrick, Emma and baby Lu) try to escape. While hiding, Emma is attacked by an infected and bitten.
9 years later, Jack and Patrick are living separately in houses next door, divided by a fence. Emma has died and Lu, now 9, is living with Jack, who she calls father. Patrick and Jack do not talk to each other, and Lu is forbidden to leave the premises. However, she bonds with Patrick’s dog between the fence.
A few days later, Patrick and his dog come across a half eaten fox. He follows the trail and sees an infected. He tries to get away but hits a fallen tree. The infected looks down on him but doesn’t see him. Instead its ears start moving and it is attracted to gun shots coming from Jack’s home. Patrick heads home, firing off shots to warn Jack. However, he attracts the infected and it attacks him. He is bitten on the neck but his dog saves him when Jack hesitates to shoot.
Lu is upset that Jack didn’t do anything to help. That night, Lu sneaks out of the house to put flowers on the dog’s grave. She is attacked by the infected but Jack gets to her in time. He is severely injured by the zombie. Patrick saves Jack and Lu, and ties up the infected. They learn that even though they were technically infected, they are immune to the disease because none of them turned. They also learn that the infected have evolved: they can’t see but they have enhanced hearing.
The next day, Lu wants to invite Patrick over for dinner and Jack agrees. Patrick talks on the radio and someone responds, prompting Patrick to want to leave. It is revealed that Patrick is her biological father. She was taken away by Jack because Patrick became an alcoholic and when Emma was attacked and killed, Patrick didn’t save her. Jack asks if they can join him and he agrees. They go to the warehouse to pick up supplies and Lu sees a woman in the distance. The guys take her home, realizing she is pregnant. She tells them that her group had heard Patrick on the radio and were on their way. However, their convoy got attacked. At this moment she hears the howling of an infected they had caught. She shoots it with Patrick’s gun and tells them the howling is how they call each other.
They start to board up the house when they hear howling in the distance. Many infected come to the house and start to attack. Fighting ensues; the woman plays music loudly, causing the infected to stop attacking and cover their ears. But the generator starts to run out of gas, causing the music to turn down. Patrick makes a decision to sacrifice himself by luring the infected away from the house. Lighting a flare, he hollers to the infected and they follow. Jack, Lu and the woman drive away as Patrick blows up himself and the infected. Jack, Lu and the woman leave town and watch the sunrise.
