In the middle of the forest, a terrified Joe runs for his life as a mysterious figure chases after him. Unfortunately Joe trips and falls, allowing the creature to catch to him. It turns out to be a vampire, who immediately starts drinking Joe’s blood.
At that moment the sun comes out and the vampire dies and turns to ash, but Joe also burns his hand, meaning he’s now the vampire. He starts moving by staying in the shadows of the trees and eventually finds a log pile, so it takes its blanket and covers himself to then run into a shed nearby for protection. There he throws up as the transformation reaches its end.
Meanwhile, Stan wakes up in his lovely home and has breakfast with his parents. Suddenly a glass falls and his mother appears incredibly sick and the house in shambles. Then his father grabs a gun and self-deletes in front of his son.
At that moment Stan wakes up, revealing his actual house isn’t in a good state. His parents are dead so he lives with his grandfather Ellis, a former soldier that always yells at him and expects to be called “sir” at all hours. If Stan even tries to ignore him, Ellis pushes him against the wall to threaten him as he complains about youth today.
As Stan leaves for school, it’s shown that the shed belongs to Ellis’ home. Stan is riding his bicycle when the gang that harasses him at school passes by, driving like maniacs to try to make him fall. Stan manages to dodge him but the distraction causes him to crash against a police truck.
Sheriff Dorney is very understanding but the deputy is furious and reminds him he’s turning eighteen soon. This means there won’t be any more juvie or second chances, he’ll finally be able to arrest Stan for good. At the school, Stan’s best friend Dommer hears the gang talking badly about him and he insults them.
This causes Marble, Pitt, and Ozzy to get angry and soon they’re pushing each other in the corridor. Roxy and Stan immediately come to his defense and Stan almost starts a fight, which is interrupted by a teacher who sends them to their classrooms. After class, Dommer says that he’s tired of this and one day he’ll finally snap and kill the gang.
He also complains about Roxy, who used to be part of their friend group but nowadays she prefers to hang out with the popular kids. Yet Stan still can’t let go of his crush. Later at home, Stan hides in the attic to look at pictures of his parents while listening to emo music and playing with his knife.
After cutting to forget, he throws the knife perfectly at a target. Then Ellis orders him to mow the lawn. When he goes outside, the dog starts barking at the shed, but Stan doesn’t understand it’s a warning and enters the shed anyway.
As he looks for the lawn mower, he finds some teeth on the table. At that moment Joe comes out of hiding and tries to attack him, causing Stan to accidentally open the window. The burning sunlight keeps Joe back and Stan rushes out of the shed to get the dog, thinking he just saw a crackhead.
Stan yells at Joe to come out and when he doesn’t, he sends the dog after him. As soon as it goes inside, the dog cries and violent sounds can be heard before its head is thrown out of the shed. A terrified Stan runs into the house to grab a knife and Ellis comes to scold him so Stan tells him about the dog and the intruder.
Ellis calls for the dog to confirm it and goes out to confront the bad guy, not listening to Stan when he says they should call the cops. The old man is devastated to see his dog dead and gives his cane to Stan before entering the shed with a wood stick, ready to kill. After some minutes of silence, Ellis announces that the place is empty except for the dog’s body, only to then start screaming.
The violence noises can be heard again and once they end, Ellis bursts through the door in a bad state. Stan tries to help him, but Joe drags Ellis back into the shed and closes the door to finish killing him. Freaking out, Stan uses the dog chain to lock the door as his grandfather’s blood leaks under the wood.
Then he runs back to the house and drinks Ellis’ beer, which usually he isn’t allowed to do. He considers calling the police, but he’s already on probation and thinks they’ll blame him for this, so instead he drops the phone and starts working on properly sealing up the cabin so Joe can’t escape and hurt others. That night, someone tries to open Stan’s bedroom door.
Thinking it may be Ellis, Stan leaves his room but finds nothing on the corridor. The power isn’t working and he hears Ellis whispering his name. He goes to check his grandfather’s room and is startled by Ellis yelling his name behind him, but there’s nobody around again.
Now the whispers come from downstairs, so Ellis follows them until he finds the shed glowing and the voice turning deeper. He gets ready to open the shed and the voice yells that Stan wanted him dead before the boy wakes up in his room. The next day at school, Roxy tries to talk to Stan, only to be interrupted by Marble who asks for help with his homework later.
Roxy knows that Stan judges her from dating Marble considering his behavior, but she admits she’s only doing it to survive the last year without being harassed. However Stan thinks these decisions don’t end with high school and will follow her all her life. Then he tries to confess what happened to Ellis, but they’re interrupted by Dommer, which annoys Stan so he leaves alone.
As Dommer leaves the school, the gang starts insulting him again and Dommer gives them double fingers. Furious, the trio starts chasing him through the woods. At home, Stan notices the shed door shaking and grabs a bat before moving closer.
Suddenly Joe makes a hole in the door and grabs Stan by the neck, allowing him to see his monstrous face. The sun soon starts burning Joe’s hands, so it’s easy for Stan to free himself and Joe goes back into hiding. At that moment Dommer arrives bleeding and yells at Stan for leaving him alone.
Stan interrupts him to explain Ellis and his dog are dead and that there’s a monster in the shed. Dommer doesn’t believe him and Stan agrees to show him, but first he grabs some things to block the door hole. Suddenly Dommer starts hearing his name and when he comes closer, Joe appears at the door.
Stan immediately rushes to cover the hole and Dommer helps him nail it down. Afterward Dommer gets excited because he thinks they can use the monster to kill the gang, but Stan thinks that’s taking it too far and forbids him from committing any murders. That night Stan goes to bed with a knife and watches an old vampire movie to learn their weaknesses.
There’s burning them with sunlight, destroying their black hearts, and decapitation. Suddenly a woman comes out from a naughty poster on the wall and sits on Stan to do the dirty with him, but she suddenly transforms in an ugly vampire and bites him, only for Stan to wake up. As he looks for his shoes, he looks under the bed and finds the vampire again, but this is a nightmare as well.
Annoyed, he tears the poster off the wall. Then he climbs on top of the shed and starts drilling holes in the roof so the sunlight can hurt Joe, but there’s still enough shadows for him to hide. Afterward Sheriff Dorney comes to see Stan to ask about Ellis and Stan says he is out, which Dorney finds strange because his car is still at the entrance.
Stan swears he doesn’t know where Ellis is and blames it on the old man’s drinking binges. Dorney explains the family living up the road had all their rabbits killed so the husband went looking for the culprit, but he never came back. When she shows him a picture of the guy, Stan recognizes Joe yet says he's never seen him.
A suspicious Dorney insists on driving Stan to school and while he gets ready, she sees Ellis’ cane on the floor. At school, Roxy worries about Stan’s wounds, but the moment is interrupted again by a nasty sexist comment from Marble. Stan comes to her defense and Marble tells him he can have Roxy, calling her “sloppy seconds”.
Furious, Stan starts punching Marble and throws him on the floor to repeatedly hit him even harder. A teacher comes to pull him back and announces they’re organizing a meeting with Ellis, but since they couldn’t find him on the phone, they’ve sent Dorney to bring him over. Fearing for the sheriff’s life, Stan runs out of the school to stop her, not noticing Marble trying to follow him.
At Ellis’ house, Dorney tries the doorbell but nobody answers. At that moment she hears a noise coming from the shed so she goes to investigate. She’s startled by something hitting the door rather hard only to then hear Ellis’ voice asking for help.
She shoots the lock but before she can open it, Stan shows up. Dorney points her gun at him and he tries to tell her it’s Joe in the shed, not Ellis, but she doesn’t believe him. Then she opens the door to save Ellis, only to be jumped on by Joe.
He bites her neck and raises her arm to waste her bullets in the air, then he rips her arm off before dragging her into the shed to feed on her. To make matters worse, Marble suddenly shows up and starts beating Stan up. After a few punches and kicks, he takes out his brass knuckles to finish the job, but he freezes when he hears a shot.
It’s Dommer, who shoots Dorney’s gun again to make Marble surrender. Stan tries calming him down, but Dommer freaks out and threatens to hurt him too if he interferes. Then he starts insulting Marble, forcing him to admit he’s a chicken before sending him to the shed.
Stan’s warnings are ignored once again and at first Marble moves normally, but he starts getting scared when he sees Dorney’s arm on the ground. Marble starts apologizing, taking the blame for every incident at school, yet Dommer tells him to go into the shed anyway. Soon they hear the noises of Marble being mauled to death.
Furious, Stan starts fighting Dommer for the gun as he yells at him. However a scream from Marble distracts Stan and Dommer hits him with the gun, knocking him out. Moments later, Roxy wakes Stan up.
Stan is nowhere to be seen and the shed door is open. Roxy says she didn’t see anyone around and starts freaking out when she sees the arm on the ground. Then Stan enters the shed to investigate and finds Marble’s brass knuckles on the floor.
In the shadows at the back, he sees Marble standing, but his dead body falls and reveals that Dommer is now a vampire. Dommer explains Joe is gone for now, but he’ll be back later to end Stan. He starts monologuing as he comes closer, not minding when small rays of light burn his body.
At that moment Roxy sees him and screams, so Dommer uses the distraction to try to attack Stan, who immediately stabs him with a stick and puts his arm under the sun to then push him away. Afterward Stan closes the shed and hugs Roxy, only to be startled by Dommer bursting out. He tries apologizing as the sun burns him to death, and Stan runs to cover him with a sheet but it's too late.
Then Stan tells Roxy everything and they start getting reading for the night. They put Stan’s body in the shed and get in the house, seal up every window and door, and start a fire in the fireplace. They also make stakes out of a bunch of sticks and gather as many knives as they can find.
Stan can’t help blaming himself for the whole deal, but Roxy promises it’s not his fault and they share a kiss. When night falls, it’s revealed Joe hide under dirt in the forest and now he’s coming out. At the house, Pitt and Ozzy knock on the door demanding to know where Marble is.
Roxy and Stan try to tell them to go away. Ozzy gets nervous when a figure appears in the shadow and tries to warn Pitt, who keeps on arguing. Suddenly an arm reaches out and drags Ozzy onto the roof to feed him, letting his blood pour out.
Pitt finally catches on and the couple has no choice but to let him in. At that moment, Joe destroys the power box. Stan thinks they should be safe there because they’ve sealed all the doors, only to realize they didn’t do the attic.
They start hearing noises upstairs so they go to investigate, splitting the group so each can check a different room at the same time. Stan finds no intruder, but he does find Ellis’ gun. Roxy is nervous as she checks under Stan’s bed, but she doesn’t find anything either.
Meanwhile Pitt finds an open window and rushes to close it, not noticing the broken glass on the floor. When he turns around, a vampirized Ozzy growls at him. At that moment Roxy is attacked and taken to the attic.
Stan runs to help her, only to find his way blocked by Ozzy and Pitt, who is also a vampire now. A scared Stan rushes into a room and locks the door with a chair to look for bullets while Pitt destroys the door with an axe. Once the gun is loaded, Stan puts it in Pitt’s mouth and shoots both vampires at the same time.
In the attic, Roxy is about to be beaten by Joe, but Stan interrupts him. He opens fire and the first bullet hurts Joe’s arm, however he can’t shoot again because Joe is fast and takes the gun away from him. Next Stan lands the axe on Joe’s shoulder, only to be kicked off.
Joe removes the axe and jumps on Stan to start choking him, however Roxy grabs the gun and shoots him as Stan is dropped to the ground. The shot only wounds Joe’s face and now the gun is out of bullets. Joe intends to attack Roxy but at that moment Stan yells at him and throws the knife he left earlier, however Joe dodges it and the knife lands on Rozy’s shoulder instead.
Next Joe tries to choke Stan again and now Roxy gains access to the axe, which she uses to decapitate Joe in one swift movement. Now it’s all over, the couple puts all the bodies in the shed and starts a fire. They wake up in the morning inside the car and they realize they didn’t lock the trunk, where something is moving to open it.
