In a small town in Spain, teenage girl Sara lives with her family, helping with her father's butcher
shop. Her mother is rather strict and doesn't let her go outside until she's done all her studying,
even in the middle of summer. While this bothers Sara, she can't deny she isn't always eager
to go out because nobody ever invites her to anything and she's constantly bullied by other
teenagers for her big-sized body, especially the popular girl clique formed by Maca, Rocío,
and Claudia. It's particularly hurtful coming from Claudia because she used to be good friends
with Sara when they were kids. These girls are so mean that one afternoon they stop by the shop to
pick up an order made by Claudia's mother and use the chance to take a picture of Sara's family to
then post it with the hashtag "the three little pigs" on Instagram. Now Sara has to stay inside
and deal with the pain inflicted by all the mean comments while the popular girls have a great time
at the local pool, where the waitress doesn't notice that the Stranger is watching everyone
carefully. The lifeguard does notice this Stranger though and calls him a clown. Later that day,
Sara's mother insists she needs to go out after studying, but her idea is for Sara to go hunting
with her dad. Sara ignores her and waits for the whole town to take the traditional afternoon nap
to go to the pool, that way nobody will be there and she can avoid being made fun of. Unfortunately
she isn't alone after all: the Stranger is there taking a swim, although at least he doesn't
comment on her bikini. The ones that do comment are the trio of popular girls, who are also around
and take the chance to make fun of Sara, calling her a piggy while making pig noises. While the
Stranger leaves the pool to get his van, Sara swims underwater to try to escape the mockery,
and since her eyes are closed she doesn't see the body of the lifeguard tied to a chair at the
bottom of the pool. When she resurfaces to take a breath, the trio puts a pool skimmer net on her
head and records it on their phones while still making fun of Sara. Once their video is done,
they run away with all of Sara's things. Now Sara has to walk down the road all wet and only in her
bikini, which gets her the attention of some boys that stop their car just to bully her some more.
Forcing herself to keep moving before things get worse, she crosses the forest area and notices the
Stranger's van, but she doesn't see a bleeding Maca crawling on the floor behind it before the
Stranger grabs her and pushes her into the van. It isn't until the vehicle takes off that Sara
sees Claudia in the back of the van asking for help, and she freezes in fear when the Stranger
opens the door. He doesn't attack her though, he just leaves a towel for her before driving away,
so Sara quickly grabs it to finally cover herself up. When she runs back into town, she's seen by
officer Carlitos, who wonders if she's ok but Sara ignores him. As soon as she makes it home,
Sara takes a shower to try to forget about what happened and is found by her mother,
who notices her sunburnt skin and scolds her for going out instead of studying even if she had been
the one that told her to go out more. Afterward, Sara rushes to her room to find some comfort in
her favorite sweets, which she keeps hidden in a box because she isn't supposed to have them,
and opens her laptop only to be reminded of the Instagram picture with all the bullying
comments. This makes her decide she won't tell the police what she saw because the bullies deserve
it. Sometime later, Sara's dad sends her to the grocery store to get some things for him and she
tries to get some of her favorite sweets too, but the cashier reminds her what her parents'
reaction would be and Sara decides to leave them. As soon as she's gone, the Stranger buys those
sweets instead. On her way back, Sara notices some commotion in town, and when her mother finds her,
she drags her with her to the pool, asking weird questions about what she may've seen earlier.
Sara finally understands what's going on when they make it to the pool and find the police there,
it turns out the waitress has disappeared and the lifeguard has been found dead, the popular
girl trio can't be found either. Knowing Sara had been there earlier, her mother forces her to talk
to the police to tell them what she may've seen, prompting Sara to lie and say she had gone to the
river, not the pool, so she could be alone and not be made fun of. She also calls her mom out
for never supporting her and doing nothing in the face of the whole neighborhood treating her
badly. When Sara stomps out of the place, Carlitos wants to follow her and ask more questions because
he remembers seeing her earlier and thinks she's lying now, but his father and superior officer
Juan makes him stay and help with the crime scene. Later in the evening, Sara's mom gives
her a different meal from the rest of the family, claiming her daughter needs to start a diet if she
doesn't want to be called a piggy. Meanwhile the Stranger is in a neighbor's house, stealing food
and killing the homeowner. After dinner, the mom finds the towel Sara brought and doesn't recognize
it, so Sara pretends she bought it at the market. Their conversation is suddenly interrupted when
Claudia's mother comes by to ask if Sara has heard from Claudia, and Sara's mom shocks everyone
by kicking her out while pointing out Claudia went from best friend to bully for Sara. Once
the woman's gone, Sara rushes to her room to have a snack but sadly she hasn't got any left, only
to find one outside her window when she checks out a weird noise. Nobody can be found outside,
thus Sara eats it anyway before making a plan to recover her phone before her parents realize she's
lost it. By distracting her dad with a drink, Sara steals his phone and takes it with her to the
forest in order to use it to make her own ring. She isn't the only one there though: Carlitos and
Juan are around looking for a lost bull. Carlitos still thinks they should interrogate Sara,
but Juan reminds him to concentrate on the task at hand. Sara doesn't notice them and proceeds with
her plan, which works well: following her ringtone allows her to find her things. The sound also gets
the Stranger's attention, making Sara freeze again when she sees him, but the man doesn't hurt her.
In fact when the missing girls' families show up in the forest tracking the phones with a special
app, the Stranger takes her into an abandoned building to protect her and touches her face
gently to keep her quiet. Once Sara understands, the Stranger escapes through the forest,
and Sara uses strategic spots in the building to hide from the families until they move deeper into
the forest when one of them finds a body. Carlitos and Juan hear the screaming and come over to check
what's going on, only to discover the body belongs to the missing waitress. The finding
of the body creates the perfect distraction for Sara to escape and get home, where she throws her
clothes in the washer to get rid of any possible clues. Unfortunately Sara's mom hears the washer
noises and comes to find her daughter trying to sneak around, so Sara lies again and pretends
she's been trying to steal cookies, which is very believable in her mother's opinion. Afterward,
Sara runs to her room and after choosing a naughty video from the internet on her phone,
she listens to it while thinking very thoroughly about the moment of closeness she had with the
Stranger. Her enjoyment is suddenly interrupted by someone throwing a little stone at her window:
it's Pedro, a friend of the missing girls. Sara agrees to meet him outside and learns he saw the
video of her in the pool because the girls sent it to the group chat, so he wants to know why
Sara lied to the police. Nervous, Sara pretends she lied because she didn't want her mother and
the cops to know about the prank video, but Pedro still doesn't believe her and tries to make her
relax by sharing his special cigarette, he also swears he deleted the video because he doesn't
agree with the way they treat her. This is Sara's first time smoking and it makes her all giggly,
prompting Pedro to push for the truth, explaining the girls' families are suspecting him since he
was the last person that had been with the trio before it all happened. Sara still refuses to
talk but promises to tell the truth if Pedro gets arrested. Meanwhile at home, Sara's mother finds
Claudia's initials and some bloodstains on the towel. At that moment, Claudia's mother finds
Sara and Pedro hanging out together and wonders if they're planning something. Pedro panics and
confesses he has a video proving Sara was at the pool, causing Claudia's mother to attack Sara as
she demands to know where her daughter is. Sara's mother hears the commotion and comes out to defend
her daughter, which ends up with both moms getting into a fight. The whole neighborhood soon comes
out too to look at what's going on including the cops, while the Stranger watches from
afar. Moments later in the police station, Sara confesses she did lie but only mentions the prank,
she still doesn't say anything about the Stranger or the girls in the van. The cops still don't
believe her and Carlitos pushes until he makes Sara cry, making her mom stop the interrogation
and leave with Sara while saying there won't be any more questions without a lawyer. On their way
out of the station, Pedro's father apologizes for his son's behavior. Meanwhile the Stranger sneaks
inside Sara's room and is found by her father, so the Stranger has no choice but to fight him until
he knocks him out. When they arrive home, Sara and her mom begin arguing: the mother
wants to know the story behind the towel while Sara cries and insists nobody understands her,
she also wishes her own family was dead. This is heard by the Stranger, who interrupts the
argument by hitting the mom and intending to go after Sara's brother next. Sara stops him before
he can kill anyone and agrees to leave with him under her mother's worrying gaze. On the street,
Sara and the Stranger come across the boys that bullied Sara the other day, so the Stranger scares
them off by almost running over them with his van. Afterward, he drives towards the forest,
and on the road, he gifts Sara her favorite sweet. Sara isn't sure if she should accept it,
she's also a bit weirded out by all the religious merch inside the van. The Stranger tries to stop
her from looking at those, and in his distraction, he doesn't notice the lost bull crossing the road,
making them crash. Since Sara passes out, the Stranger carries her to his hideout and even takes
care of her wounds. When Sara wakes up a few hours later, she finds herself inside an abattoir and to
her surprise, Claudia and Rocío are there too, still alive but tied up. As Claudia calls Sara
out for not telling the police about this, Sara tries to untie the girls, but she only manages to
remove the gag before she must run and hide when the Stranger comes back. The fact the gags are
missing doesn't go unnoticed and the Stranger hurts Claudia until she confesses Sara did it
and she's now hiding. The Stranger immediately goes after her, so Sara runs through various
corridors until she accidentally trips and comes across Maca's body. Sara screams at the sight,
allowing the Stranger to find her and bring her back to the main room, making sure to be gentle
to Sara again as he calms her down and explains he won't hurt her. Then, he grabs his knife and
puts it in Sara's hand, telling her they can kill her bullies together. Sara actually hesitates for
a moment as she considers the offer, but in the end she chooses to do the right thing and attacks
the Stranger instead. It's not hard for him to hit Sara and push her away, but since he's distracted,
Claudia takes the chance to kick him as well. Sara sees this opportunity and stabs the Stranger,
who immediately fights back, and during the struggle, a weapon he left nearby is
shot by accident, causing Claudia to lose a hand. Ignoring the screaming, Sara continues
to attack the Stranger until she kills him, but as soon as she realizes what she's done,
she begins crying in denial - she can't believe she took a life and that it was the life of the
only person that ever was nice to her. Once she calms down, Sara grabs the stranger's weapon and
shoots at the girls, but it isn't until she's left that it's revealed she didn't kill them,
she only released them by shooting their ropes. In the middle of the road, Sara comes across Pedro on
his bike, who offers to take her back to town without questioning the blood on her clothes.