Tired of being quarantined, Aidan apologizes to his camera, saying he’s tried. Then he gets the rope ready to self-delete. This all started 42 days ago.
When Aidan wakes up, the woman he spent the night with is already gone. He goes to the bathroom to wash up and finds a note from his parents with a cheque, reminding him to pay rent. He can hear yelling and pounding in the hallway but thinks it’s just the neighbors being themselves.
When he turns on the TV, he finds the emergency broadcast system. Suddenly sirens and screaming can be heard on the streets. Aidan runs to his balcony and sees a smoking helicopter crashing against a building.
People are running everywhere and a lost girl asks for help, but suddenly she and a man jump on an elderly person to kill them. After a military jet flies by, a horrified Aidan rushes back inside at the same time his neighbor Brandon enters the apartment. He says that his roommate, whom he has known all his life, suddenly attacked him.
On TV, a man explains that a new virus is on the loose that transforms people into flesh-eating zombies. It’s transmitted through blood, mainly through bites and scratches. Before the man can say more, the transmission ends.
Realizing that Branon was wounded by his roommate, Aidan grabs a knife to defend himself. As people in the corridor keep yelling and pounding on doors, Brandon’s eyes start bleeding and his face begins transforming. Aidan forces him to leave and he has to run to push the door closed because Brandon finally snaps, trying to reach inside to attack him.
After lots of effort Aidan manages to lock the door and looks through the peephole, horrified to discover people eating each other in the hallway. He immediately steps back and tries to put himself together. On TV, they explain that the virus is taking over the world and tell people to stay home.
Aidan starts drinking while trying to call his family but the phone lines are down. Eventually he gets a bunch of delayed texts from his father, saying he and his mom were going to see him but they didn’t have news about his sister. However another text has an apology because they couldn’t make it and they ask Aidan to stay alive.
The last text is from his mother telling him to call them, but when he tries the lines still don’t work. Aidan has a breakdown and spends most of his day crying while staring at the world. Later he decides to start counting the pandemic days and writes reminders on post-its.
He can’t stop thinking about his father and their time together. On day six, Aidan starts to move things around the house, desperate for a change. Experts on TV talk about the effects the quarantine is having on people’s brains.
On day seven, he tries recording a video log but people are still screaming and attacking each other in the hallway, making terrifying noises that kill the moment. Aidan tries to explain how these non-stop noises have been affecting him but he ends up closing the computer. On day fourteen, Aidan covers up all the windows so he can avoid seeing the state of the city but he won’t turn off the news.
Experts have named the zombies “screamers” and explain that they repeat the last words said before turning. Aidan keeps on drinking and whenever someone pounds on his door, he ignores them. On day sixteen, Aidan discovers he has no water and throws things in frustration.
He knows he should go out for supplies or try to find his family, but he doesn’t dare because he can still hear the people dying outside. Aidan reads about sensory deprivation and how it can make people hallucinate, so he tries to keep himself busy by playing guitar or practicing sports. However he’s so frustrated that he ends up breaking a mirror.
One night he hears noises in the bathroom and gets his bat ready, but he immediately rushes to hide when he discovers that a screamer has broken into his apartment through the vents. The woman keeps repeating “no” as she searches the apartment so Aidan waits for the right moment to move behind her and strike her with his bat. The screamer collapses and Aidan has to deal with having killed a person.
After throwing the body off the balcony, he puts a surfboard under the bathroom vent to block it. On day forty-two, Aidan records another log while still hearing screaming outside. He explains he’s losing his mind and how he’s too scared to go out.
In three days he’ll begin starving, so he needs supplies. Suddenly his phone rings and Aidan hears a voicemail from his parents. They were locked in at the office and couldn’t get in contact with him or his sister.
The message was cut short when a screamer found and killed the couple. Hearing his parents die causes Aidan to have his biggest breakdown yet. Desperate for an outlet, he grabs his bat and leaves the apartment to find Brandon on the floor repeating “I’m okay”.
Aidan gets ready to strike him, but he can’t bring himself to do it. At that moment a bunch of screamers try to attack him, so he moves quickly to dodge them and runs as fast as he can. Since the screamers are blocking the way, Aidan takes the stairs to the lower floor and waits for some runners to pass by before taking the corridor.
He pushes off any person who tries to attack him and eventually he reaches the other stairs, which he climbs to return to his floor. Now he can reach his apartment from the opposite corridor and quickly pushes his fridge to block the front door. Looking through the peephole shows the screamers looking for him.
Moments later Aidan hears a loud noise and the power goes out in his apartment. When he looks out the window, he discovers the whole city has lost power. He spends the night dreaming about his family and in the morning, he wakes up to the screamer noises in the corridor.
Tired of all this, Aidan decides to self-delete. However he stops the process when he notices that a woman in an apartment across the yard is still healthy. Afterward Aidan records his last log because his battery is dying, saying he’s met a girl.
He cuts his beard and makes a plan to contact the woman, hoping to help her. When he goes to the balcony, he sees that there are screamers in the woman’s building too and immediately hides. Still determined to make contact, he writes on signs that he puts up on the window and she finally sees him too.
He learns her name is Eva, she’s alone, and she doesn’t have many supplies left. She has to close her curtains when she hears screamers coming but agrees to talk to him later. That night it starts raining, so Aidan puts a bunch of pots out to collect water before washing up and shaving, unaware Eva looks at him for a few seconds.
The next day Aidan and Eva communicate with signs to make a plan. They connect their balconies with rope and he sends her some water bottles. At that moment a screamer begins climbing Eva’s building but when he’s about to reach her, Aidan throws a glass bottle at his head and starts banging on his railing to get the guy’s attention.
That screamer starts climbing Aidan’s building instead while another screamer pounds on the door so hard that the fridge is beginning to move. Eva also throws things, but Aidan keeps the screamer’s attention on him until the guy reaches his balcony. Then Aidan goes back into the apartment and locks the balcony door before rushing to push the fridge against the front door.
The screamer outside begins pounding on the window to break it but the wound makes him collapse, so Aidan uses the chance to run back outside and beat him up with the bat. Now there’s blood on his shirt so he quickly takes it off. Moments later Aidan prepares a bag and leaves the apartment to take Brandon’s keys from his body.
Screamers appear in the corridor so Aidan lies down on the floor to pretend he’s dead until they’re gone. Then he enters Brandon’s apartment, closing the door right before the screamers reach him. Inside, there are bloodstains on the walls and a body on the bed.
Aidan takes the few food supplies he can find and is surprised to find some climbing equipment as well, although the axe is missing. He checks the bedroom and finds it under the bed, but at that moment a screamer comes out of the bathroom. Aidan pushes him against a mirror and tries to run, but the screamer tackles him against the wall.
Grabbing a lamp, Aidan hits him a few times to get him off him and falls on the bed, where the body is waking up too. The screamer jumps on him and fails to bite him through his clothes, giving Aidan time to grab the axe and finally kill him. After killing the screamer on the bed too, Aidan takes all the climbing equipment and tries to leave, but the corridor is full of screamers.
He carefully sneaks around and manages to dodge a screamer at the last second to return to his apartment, where he immediately takes off all his dirty clothes. When he checks the climbing equipment, he’s excited to find two walkie-talkies. Afterward Aidan ties some sheets on his balcony to climb down and safely reaches the ground, where he finds eaten bodies.
There are running screamers as well, so Aidan sneaks around and quickly throws a walkie-talkie at Eva’s balcony before running to climb back to his place. The next morning Eva contacts Aidan and they’re both so excited to finally have a conversation again that they spend the rest of the day talking about random things. Slowly gaining back hope, Aidan decides to search for supplies again, this time leaving through the vents.
He’s startled by a zombified face, but it’s just a dead screamer. He manages to enter the bathroom of another apartment and notices blood on the side of the tub, but when he moves the curtains he finds it empty. Then he checks every room and after making sure he’s alone, he opens the cupboard to luckily find lots of food.
Aidan has a snack before calling Eva to share the news with such excitement that he’s already making plans to escape and find their families. Eva explains there are screamers at her wall every day and she’s tired of it, so she’s built a rope out of sheets like he did and wants to move to his place. Things get tense when Aidan finds the fridge against the front door, which means someone lives there.
He checks a door that he didn’t see before and discovers a hole in the wall. Suddenly Edward appears in the kitchen with an improvised weapon he made. He puts it down when he confirms Aidan isn’t a screamer and explains he came from another apartment through the hole some weeks ago.
The owner self-deleted in the tub and Edward threw the body in the hall. The old man shares some meat he cured himself and lets Aidan take food from the cupboard. They discuss the situation and get philosophical about loneliness and having to kill other humans to survive.
When Aidan turns around to grab more food, Edward hits him with the bat to knock him out. Minutes later Aidan wakes up in Edward’s bedroom, where he’s keeping his infected wife. Edward wants to use him as zombie food but his wife wouldn’t attack an unconscious body, so he tied Aidan up and waited for him to wake up.
He wants Aidan to take some medicine to avoid feeling any pain and Aidan thinks he already did this to their neighbor. However Edward swears he really found the man dead in the tub but his wife wouldn’t touch him, so he had to feed her his two dogs. Suddenly Eva yells through the walkie-talkie and Edward moves to check on the noise.
Aidan struggles against the bed until he breaks it and frees himself, then he pulls Edward back into the room until he becomes his wife’s dinner. When he picks up the walkie-talkie, Eva tells him the screamers have entered her place. Aidan immediately runs out of the apartment and the screamers chase him down the corridor.
He can’t enter his place because of the fridge so he goes into Brandon’s instead. He looks outside and sees Eva hiding on her balcony while the screamers pound on the glass doors. Very carefully, Aidan jumps from Brandon’s balcony to his own and now he can use the sheets to climb down.
However the sheets slip and he falls until he painfully lands on a chair. The noise gets the attention of a screamer who quickly comes after him. Aidan finds a gun next to a body and grabs it to shoot the man in the head.
As screamers jump from other balconies, he shoots another enemy to clear the way. Eva throws her sheets and Aidan starts climbing, but so does a screamer. Aidan has no choice but to jump on a different balcony and cut the sheets to make the screamer fall.
Now Eva can climb down to meet with Aidan on the lower floor with a tight hug. The duo goes inside the apartment and screamers come in when they open the door, but they go past them and lock up, leaving them inside. There are more creatures in the corridors so they rush to the stairs and Aidan destroys the door handle with his bat.
A zombified man on the steps can barely move so the duo decides to spare him and moves to the next floor. When they open the door two screamers tackle Aidan against the wall and Eva pushes one down the stairs, but unfortunately Aidan and the other creature fall too. The screamer tries to bite Aidan until Eva kills him with the axe.
Then the duo takes the corridor and begins running as fast as they can, hitting and pushing off all the screamers that try to attack them. This corridor connects both buildings and Eva manages to enter Aidan’s apartment, but he’s jumped on by the screamer that has been outside his door since the beginning. This terrifying man tries to reach inside, however Aidan manages to pull him back and finally kill him.
Afterward Aidan enters the apartment and starts taking off his clothes, thinking he’s been bitten. He goes to the balcony to self-delete but when he removes his last shirt, he finds no wounds. They don’t have time to celebrate because there are screamers at the door, so they rush to push the fridge while promising to work together to survive.
