In the near future, the damage to Earth’s environment has caused a new Ice Age to take over
the planet, and now humanity must live underground to survive. In one of the few remaining outposts,
an alarm rings and yelling can be heard before two terrified people begin running down the
hall because something dangerous is going after them. They reach the door but sadly it’s locked,
and the duo is killed by their chaser. Meanwhile in another outpost, Sam is outside fixing the
satellite dishes when he notices a few men come out. The sick guy asks for one more day
to recover, but Mason thinks they’ve already wasted enough resources on him and gets ready
to shoot him, ignoring the fact the guy is asking for “the walk”. Sam interrupts them and reminds
Mason that sick people get the choice to walk away or get shot, which should be respected,
but Mason doesn’t care and kills the guy anyway, saying it’s for the sake of their survival. As
Sam returns inside, it’s revealed that because these few survivors live in a confined space
with limited resources, they’ve become scared of the common cold. The last time they had the flu,
it killed twenty people in less than a week. That’s when their leader Briggs made a new rule:
if someone gets sick, they go into quarantine. If they don’t get better, they get to choose between
a bullet or a long walk in the snow. The people in this outpost work hard to take care of each
other and keep on growing seeds, but they aren’t the hundreds they were in the beginning because
food gets more scarce every year. There are rumors of a paradise with warm weather, but Sam doesn’t
believe them. Sam goes to see Briggs to tell him about Mason breaking the rules, and while
Briggs isn’t happy with what he’s hearing, there’s something more urgent he must take care of first.
They go into the communications room and Cooper informs them they received a SOS loop from Colony
5 yet they aren’t answering any messages. Briggs calls for an emergency meeting in half an hour
while Sam goes to see Viktor, who is in charge of the livestock. Unfortunately he also has bad news:
the last litter of rabbits was stillborn, and of the twelve remaining ones, there’s only one
female that the other rabbits don’t want to mate with. Meanwhile Briggs goes to see Mason to scold
him for what he did, but Mason still defends his decision, saying walkers will just come back and
take their food. Afterward, Sam goes to see his girlfriend Kai, who gets him some pellets for the
rabbits while talking about her work. She thinks working weather modification tech exists and it’s
buried somewhere under the ice, so she’ll continue to search for it with their radar to never lose
hope. Moments later, the survivors gather for the meeting. Dexter reminds his wife not to cough,
and when Sam walks by, he notices they aren’t well and tells them to go to their rooms, but Dexter
says they’re fine. At that moment Briggs comes in and informs everyone of the situation with Colony
5, announcing he’ll lead a team to go check on them. Mason protests, saying they shouldn’t spare
resources or people in these hard times, but he’s ignored. Then Briggs asks Dexter to join the team,
so to save him, Sam volunteers to take his place, saying Dexter must stay with the turbines. Graydon
also volunteers, ignoring the protests of his father Viktor. With his team completed, Briggs
leaves Kai in charge until they get back. Suddenly Dexter’s wife sneezes, and the people cover their
faces as they step away from them. The couple is immediately quarantined and Mason complains again,
saying they should put them to the test and that Kai can’t be a strong leader. Briggs scolds him
and tells him to wait for his return to decide anything about the sick couple. Under a snowstorm,
a boy keeps walking against the wind until he’s shocked to find his mother dead on the ground.
At that moment Sam wakes up, revealing that was a nightmare about his mom’s death. Kai comforts
him and reminds him it wasn’t his fault. The next day, the team leaves on their mission,
meaning they have to walk a lot while enduring the freezing snow and the wind. After crossing
an abandoned city, they find an old weather modification machine, but unfortunately it isn’t
working. Moments later, they reach a bridge and cross it as carefully as they can, which is harder
than it sounds because of the damage it took through the years. They walk around the gaps and
Briggs almost falls when a piece of bridge breaks under his feet, but he moves away just in time.
At the end of the bridge, they find a car with a dead man next to it and a gun in his hand. When
they take a closer look, they find the family dead inside the car and realize the man killed them all
before self-deleting. After lots of walking on the snow, the trio finds a crashed helicopter and gets
inside to use it as shelter for the night. Graydon is so young that he’s never seen a helicopter or
plane in the air and he’s amazed by the idea. Briggs calls their outpost for an update, and
Cooper informs him that Dexter and his wife are getting worse. Mason keeps asking to test them,
so Briggs gives Cooper permission to use force against Mason if he crosses a line. Afterward,
Graydon finds a dirty magazine and the others tease him for how much he likes it. Briggs also
points out this place is close to the spot where he found Sam, who proceeds to share his story with
Graydon. When he was a kid, his family and other survivors were hiding in the mines. After they ran
out of supplies and ate the dogs and the horses, his dad and other men went to the city to get help
but never came back. People in the shelter started to die out, so Sam tried to get his mother and
his sister to a safer place. Unfortunately they got hit by a snowstorm and they got separated,
so Sam never saw them again. He would be dead too if Briggs hadn’t found him. The next day,
they finally make it to Colony 5 and are shocked to find blood outside the main entrance. When they
come inside, they can also smell smoke. The trio goes down the stairs and finds even more blood
as it’s revealed this is the corridor from the beginning. This colony was supposed to have fifty
people in it, so the fact nobody is welcoming them is worrisome too. Briggs gives Gradyon a gun just
in case then the trio keeps on looking around, finding blood on the ground and rooms crashed no
matter what corridor they take. They’re ready to accept everyone is dead when suddenly they
hear a noise coming from a locked room. Sam picks the lock and when they open it, they find a man
on the ground. They approach him slowly, only for Leland to suddenly yell at them, asking for mercy.
The trio promises they’re friendly and Leland asks them to close the door again before accepting some
food and water. He’s been stuck in here for many days and he isn’t sure if anyone else is alive,
he also explains that a few days ago his colony fixed their antenna and received a message that
he plays for the trio now. On the screen, a man appears in an area without snow explaining that
his group has repaired a weather machine and successfully melted the permafrost, so now they
have access to fertile ground. The only thing they need now is seeds. Unfortunately the transmission
cuts off and they only get to hear half of the location. Leland tells them that they triangulated
the transmission and sent a team to find this warm area, but they never found it. Something dangerous
found them instead and followed them back to the colony. Sam asks Leland to mark the location on
his map, then Briggs tells him that they'll take him back with them. However Leland is too scared
to leave the room and reveals he didn’t make the noise they heard. The trio takes all the supplies
they can find in the room and tries to get in contact with their colony to no avail. Then they
finally leave and try to drag Leland with them, but some weird noises can be heard and Leland
gets so scared that he runs back inside and locks the door. The trio continues to move without him,
and the deeper inside the outpost they go, the more banging and screaming they hear. Eventually
they see the light from some torches and come closer to find a disturbing sight: surrounded
by the bodies of the colonists, there’s a man butchering a body and others feeding on human
flesh. Suddenly the butcher smells them and turns around ready to attack, but Sam shoots him first.
The shot causes more cannibals to wake up from the pile of bodies and the leader screams as they
start chasing the group down the corridors. Sam shoots the leader in the ear and manages to kill
another guy, but there are too many of them, so Briggs throws a dynamite stick to slow them down.
Graydon accidentally splits from the group, but he barely manages to step back before he’s surrounded
by cannibals who immediately attack him. Briggs and Sam finally show up and fight against the
attackers, killing them one by one until they’re all dead. Unfortunately by the time they check on
Gradyon it’s too late: he’s dead as well. There’s no time to grieve, Briggs and Sam have to keep
on running. After climbing the stairs, Sam shoots another cannibal and runs out of ammo, then Briggs
breaks the stairs off to stop the cannibals from following them. Unfortunately there’s a cannibal
already there, so Briggs proceeds to fight him and after lots of struggle, he manages to shoot
him off. The rest of the cannibals soon arrive and see what Briggs did, so the leader yells at him
in fury. Once the duo is outside, Briggs throws dynamite into the entrance to destroy this tower
and seal the colony. They walk under the snow for a while and when they find the helicopter again,
Briggs decides they’ll spend the night in it because the temperature is dropping too fast. They
begin discussing the cannibals and Briggs says that that people do terrible things to survive,
then he shares a story about his time in the army. During the relief, twenty thousand people were
corralled in a stadium. The soldiers handed out food and the doctors treated the sick,
but when the food ran out, people with guns started taking things from people without guns.
Soon there was nothing to take so the higher-ups started to decide who lived and who died. Mason
was part of Briggs’ squad back then and they left that shelter together to find a place where that
kind of trouble would never happen. The next morning, the duo discovers that the cannibals
have been following their footprints and are now coming closer. Sam is afraid that they'll follow
them to the colony, but Briggs has a plan to stop them. They run through the bridge as fast
as possible and make a difficult jump to cross more quickly, then they leave some lit dynamite
next to the gap and hide behind some broken signs. Unfortunately the wind puts out the fuse,
and when Sam volunteers to light it again, Briggs knocks him down and goes himself. The wind makes
it very hard to use his lighter, but Briggs keeps trying while a few cannibals try to jump and fall
through the gap. Once Briggs finally lights the fuse, he fights the cannibals on purpose to bring
them closer, and suddenly the dynamite blows out in his hands. The explosion kills Briggs
and takes down the middle of the bridge, so now it can’t be crossed anymore. Sam sees that a few
cannibals including the leader have survived and glare at him from the other side, so he
starts running again. Meanwhile at the outpost, Mason has taken Dexter and his wife outside,
ignoring their pleas for mercy. Mason shoots the wife, but before he can shoot Dexter too,
Kai comes out and threatens to shoot him if he doesn’t stop. An argument ensues over how the
colony should be led, but at that moment they hear Sam crying out for help. Dexter uses the
distraction to run away and Kai runs to check on Sam, who passes out from the cold. Mason
approaches too and knocks Kai out. A few hours later, Sam wakes up inside the outpost and he
has to give Viktor the bad news about his son. Suddenly Mason comes in and cuffs Sam to the bed,
saying that there has been a change in command and using the excuse of survival. Rations will
be cut in half, anyone showing signs of sickness will be tested immediately, and whoever refuses
to work won’t eat. Sam tells Mason everything that happened and insists they should leave before the
cannibals find them, mentioning the warm place he saw in the video. However Mason doesn’t believe
him and leaves the room, taking everyone with him. Before leaving, a little boy reveals that he
stole the handcuff keys and secretly hands them to Sam. Outside, Mason and Viktor keep an eye
out for possible invaders but see nothing. Viktor points out that Sam isn’t the kind to lie, so they
should be ready for an attack anyway. They decide to use the security cameras instead, but they’re
interrupted when another colonist informs them Sam has escaped. Back to Sam, he goes looking for Kai
and finds her restrained in another room. After quickly releasing her, he uses her computer to
look for the location of the message. At first he sees nothing, but after looking around the radar
finally picks up a warm area, confirming a thaw exists. The couple takes as many seeds as they can
carry in their bags and runs to tell the others, only to be intercepted by Mason and his men,
who remind him who is in charge. Suddenly, there’s a loud banging noise outside, so the group runs
to check the security cameras. To their horror, they see the cannibals hitting the doors to try to
bring them down, and the leader holds up Dexter’s head as a threat before breaking the camera.
Finally believing Sam, Mason quickly gives orders: everyone that can shoot must be given a weapon and
the rest of the people shall hide in the vault. While Cooper guides all the colonists to the vault
and guards the door, the armed group runs to the corridor to wait for the door to come down. For
a moment the lights go out, and when they return, the door opens yet nobody comes in. Now the noises
can be heard inside the shelter, and suddenly a cannibal burst out of the vents right in front
of Cooper. He tries to defend himself but the cannibal knocks him down and runs to the vault,
only for the colonists to close it on his face. In another corridor, a lost girl is looking for
shelter but a cannibal finds her and kills her. The armed group realizes the cannibals are in the
vents too late because the enemy finds them as well. A very fierce fight ensues with both sides
losing people, but no matter how many cannibals they kill, more keep coming. Sam and Kai run away,
but Viktor is tired of running and battles against the leader. He puts up a good fight,
but sadly the leader kills him first. Meanwhile a wounded Mason runs to a safe
room where a few survivors that didn’t make it to the vault are hiding, closing the door before Sam
and Kai can enter too. A cannibal is getting closer, so a colonist knocks Mason down and
lets the couple come in, but unfortunately the cannibal manages to follow them into the room.
Kai immediately shoots him down and they run to lock the door, but it won’t hold for long because
the rest of the cannibals arrive and start hitting it. Thinking fast, Sam opens a vent and tells the
group to follow him outside. Mason protests, saying they’ll only freeze off and that they
should hold off the enemy here. The others ignore him and leave through the vent, and Sam pauses to
give Mason a gun before leaving too. In just a few seconds, the cannibals break the door down
and come after Mason, who shoots a tank of gas to create a huge explosion. All the cannibals
are killed except for the leader, who hides inside the vent just in time. Soon the leader reaches Sam
and they start fighting inside the vent, which breaks under their clashing and causes them to
fall into the livestock room. The fight continues as Sam keeps on throwing anything he can grab at
the cannibal, but the guy easily overpowers him and begins beating him up. After a few hits,
the cannibal throws Sam on the floor and begins dragging him around, which gives Sam the chance to
grab a fallen knife and hurt his opponent on the leg. The guy tries to defend himself but this time
is Sam who overpowers him and starts beating him up, furiously deforming his face before cutting
his head off at the mouth. Then he tries to leave, only to find the corridor on fire. Outside,
Kai and the remaining survivors come out of the vent and watch their home burn. At that moment,
Sam comes out of the vent too and tells them they need to find the warm place
from the message. The group starts walking on the snow, hoping they’ll find a new home soon.