The movie opens up with a married woman, Patricia, preparing food in the kitchen, and it seems to be a normal day for her. But little did she know that her entire life is about to be turned upside down. Her husband, David, suddenly arrives in the kitchen, looking anxious, and asks her to run away.
This obviously confuses Patricia and she looks at him in shock, at which point David goes insane, and violently stabs her, and beats her with the hot pan. Sadly, before she gets the chance to run away, David oddly says it’s not him, before he stabs her multiple times with the sharp knife, ending her life, while a child is seen locked in a cage-like room. Later we hear from a podcast that when the police arrive at the crime scene, they find David with the murder weapon; he is staring at his wife’s dead body with a blank expression.
The police then search the house and make a horrifying discovery: David's daughter, Michal, is locked in a cage-like room and it seems like she hasn’t seen sunlight for years. Because David kept mentioning that someone was controlling him, he is labeled "The Puppetman Killer. " He is also sentenced to death by lethal injection.
The scene now fasts forward to the present; Michal is now a college student, and she shares a room with Charlie, her best friend. They've just finished listening to a podcast about Michal's father, which has gone viral as his execution date approaches. We learn that Michal can’t even remember how it happened, but she has not been able to put her gruesome past behind.
She still struggles with the fact that her father is a cold-hearted killer. Although life for Michal is very disturbing, her roommate, Charlie, finds it very fascinating. Based on her research, she discovers that the police found satanic books when they arrested Michal’s dad.
Michal is obviously annoyed by this rumor, but she doesn’t react as Charlie is her best friend. At college, we are introduced to their friends, Jo, who is a medical student, and Glenn, the cocky gym rat, and there's also Michal’s boyfriend, Danny. They are nearing the end of the semester, and want to throw a small party in secret on the dorm's rooftop.
One night, Charlie can't stop thinking about "The Puppetman Killer;" she even secretly begins to explore if Michal might have inherited any of her father's tendencies. Michal’s father, David, will receive a lethal injection that week, and Charlie spends a good chunk of her day researching different articles written on the case and studying them. Meanwhile, Michal will always have the same nightmare about when she was a little girl, and she is awakened by Charlie while sleepwalking.
It turns out this isn’t the first time she's had this nightmare that causes her to sleepwalk, during which she always draws three cryptic lines on the wall with her hand wound. To add, this wound she got was caused by her habit of scratching her hand, and the symbol is the same one that she frequently sees in her dreams. As the days pass, Michal notices something unsettling; wherever she goes, she is surrounded by a large number of black ravens.
This indicates that something very bad is about to happen. They head to a local liquor store, and manage to buy a lot of alcohol, despite the fact that they are minors. Later, Danny accompanies Michal to her room but refuses to enter, before walking away after wishing her a goodbye.
Following this, when Michal is alone in her room, she hears messages popping up on Charlie’s laptop. Curiosity gets the best of her so she decides to check it. To Michal’s shock, she discovers a folder full of her sleepwalking videos.
She checks a few of them, and finds herself doing it every night, and Michal recording it as a documentary. Right then, Charlie arrives in the room, and is taken aback to see Michal using her laptop. When the latter asks her about the recordings, Charlie defends herself saying that she did it for her safety, and was always there to help her.
She also assures Michal that she has kept it a secret from everyone else. At night, Michal, Charlie, and their friends Jo, Glenn, and Danny gather on their dorm’s roof for their party. At first, everyone seems to be having a lot of fun as they make new resolutions and share stories.
But when Glenn gets excessively drunk, he inadvertently talks about Michal’s dad and her sleepwalking habit. This shocks our girl, as she realizes that Charlie has exposed private details about her life. The latter once again swears that she was just trying to help, but Michal is having none of it.
But then all of a sudden, Charlie suddenly becomes paralyzed, almost as if something has taken over her. She continuously says that she cannot move, but her friends believe that she is simply faking it. To make matters worse, Charlie walks backwards, and falls off the terrace.
She dies on the spot, while her friends are left completely speechless by what they just witnessed. In the next scene, Michal can be seen talking to the investigating officer about Charlie’s death. She mentions that she saw fear in Charlie’s eyes before she fell and it was due to her; it was like she was afraid of Michal.
As Michal walks home, she notices what looks like a group of ravens following her. That night, Michal cannot sleep, because black ravens are smashing against her window one after another, and this scares the life out of her. As the days pass, her friends grow increasingly worried for her; Danny, in particular, seems to be the most affected, so he decides to check up on her.
He goes to her dorm and knocks, but she ignores him, so he decides to wait for her outside her room. Hours pass by and he eventually falls asleep. In the middle of the night however, he is woken up by a loud thud.
He notices that the door is open, but there is no one inside the room. Danny quickly realizes that Michal is sleepwalking again, so he runs up to the terrace, where he finds her on the edge. Thankfully, he manages to stop her before she can take a leap.
Later, the group learns from Chalie’s mother that Charlie used to have regular meetings with a psychic woman named Ruby. She invites them over to her house to discuss something very important. The group is a bit skeptical about this, but they accept as they are desperate for answers.
At first, Michal is asked to wait in the living room, while Ruby tells the others something shocking. She reveals that Charlie used to visit her because she was scared. When the group asks what she was scared of, she says ‘Michal’.
Meanwhile, Michal notices a book titled "The Cult of Dolos" in the living room. It has the same symbol on the cover that Michal draws with her blood when she has bad dreams, and she regularly sees it in her nightmares. Just then, the psychic calls her into her room.
To find out the truth about Charlie's death, they conduct a seance under Ruby's guidance. This will allow them to contact Michal's late mother, Patricia. They believe that she holds crucial information about who is responsible for Charlie's tragic demise.
During the seance, a spirit suddenly possesses Ruby, and makes her write a spine-tingling confession; "I killed Charlie”. Seeing this, Michal is shocked to the core. She then becomes angry and demands to know the identity of the spirit, and Ruby looks very scared of her.
The spirit possesses Ruby again, and to her horror, Ruby writes ‘I am Michal. ’ Upon seeing this, Michal finds it hard to believe she was the one who killed her best friend. Out of her three friends, only Danny believes what Ruby has shown them.
Michal seems to have something inside her, and Charlie was its first victim because she was becoming a problem. Later, Jo makes a startling discovery on Charlie's laptop; she finds out that a book titled "The Cult of Dolos" had somehow led Charlie to Ruby. At that moment, Michal begins sleepwalking again; this time her pattern is more unusual than ever.
Her friends witness this from a distance, and finally realize that something sinister is going on. Jo, who had been denying this nonsense from the start, becomes so intrigued that she secretly meets with the psychic, and borrows the book from her. Ruby warns her that Michal can’t know that Jo has this book.
Afterwards, she asks Glenn and Danny to come over so that they can solve the mystery together. However, Glenn ignores her message as he’s busy with his gym stuff, while Danny can’t come right now as he is with Michal. Left with no options, Jo decides to investigate the matter herself.
She visits a silent library at night and begins reading the book alone. As Jo goes through its contents, she discovers a chilling ritual to summon a malevolent demon into the world, and involves a union of light and dark, innocence and sin. Those who conspire against the demon shall bend to his will, ceding control to his will.
This slightly scares Jo, and she calls Ruby to ask if they are in danger. However, it is too late… The demon has already taken over her and Jo loses control of her own body. The demon forces Jo to stab herself with a pen, and cigarette that she was smoking falls onto the book, and it quickly catches fire.
At last, her face is pulled towards the flames, and she is burnt to death in a horrifying manner. Simultaneously, at the gym, Dolos suddenly takes control of Glenn's body, compelling him to add heavy weights to his lifting bar. The poor guy then unwillingly sits under it, and tries to lift the bar.
As it is very heavy, he meets a tragic demise as his face is crushed. Meanwhile, Danny takes Michal to see her dad in prison, and they are completely unaware that their friends have been killed. The father-daughter duo finally meets after all these years, but their union is rather tense.
Without wasting any time, Michal asks why he killed her mother, but he claims that he didn’t. He was controlled by someone else, and that someone was none other than Michal. He then reveals that years ago, he and Patricia participated in the ritual that was described in the book in order to gain the demon’s power.
But since it required a mix of innocence and sin, they also included a young Michal by offering her blood as well. Once the ritual was complete, Dolos was brought into the mortal world. Patricia wanted to offer her body, but the demon tricked her and instead chose Michal’s body as a vessel.
The father adds that when he was about to kill Patricia, he heard Michal whisper to him, ordering him to grab the knife and stab Patricia. This explains why Charlie looks at Michal like she was afraid of Michal prior to her death. Hearing all this, she is left completely speechless.
Furthermore, the demon is what Michal is; if Michal feels enraged, the demon will feel the same way. Later while returning to the dorm, Danny tries to comfort a grieving Michal, but an invisible force prevents him from touching her. He then gets a call from the police, revealing that 2 of his friends are dead.
The news comes as a shock for Michal, and here Michal starts to hate herself and tells Danny to stay away from her to keep him safe from death. Michal is at a loss for what to do to put an end to this madness, plunging her into a state of depression. At one point, she decides to end her life, but… A new strange thing happens when all the speeding vehicles on the road suddenly stop to let her pass.
As if that wasn’t enough, Michal tries to find another way; she gets up on a bridge, and decides to jump off. Danny who is searching for her, witnesses the malevolent spirit within her, Dolos, stop her from taking such a drastic step, throwing her back to the bridge. Seeing her suffering, Danny proceeds to contact the only person who can help them, Ruby.
Unfortunately, even the psychic has become scared at this point after hearing Danny’s story. She fears that Dolos will find out about her, which will result in her death. Hence, Ruby starts claiming that everything she said up to this point was a lie.
She even returns their money, saying she has realized her mistakes. Ruby claims that Michal is totally fine, and there is nothing wrong with her. This makes the duo realize that they are on their own now, and they leave the place to find other solutions.
Ruby then calls the chief detective: Al, and informs him about the situation. Later, as the couple are on their way home, the entity inside Michal's body wonders what Ruby gave him, but Danny informs her that it's nothing. Seeing Danny keep hiding something, Dolos the devil takes over him; the poor guy is forced to break his own fingers.
Danny suddenly takes out the money Ruby gave him, and we see that she left some warning notes for him, which the demon tells Danny to read for her. Upon learning this, he makes Danny slam his head repeatedly against the steering wheel, while Michal watches all this unfold, but she is helpless to intervene. She knows that she is the one responsible for this, as the monster inside of her doesn’t want anyone to know about their secret, and Danny becomes Dolos’ latest victim.
Shattered by the loss of her best friend, a bloodied Michal goes to the police station. When an officer asks what's the matter, she says that she’s killed many people. She then demands he shoot her immediately.
Unfortunately, as the poor guy contemplates on what to do, Dolos takes control of his body and kills him. Several other officers rush to the scene, and we see Michal is happy, knowing that the police will end her life and all this craziness. But all of a sudden, They all meet the same fate.
Detective Al then approaches Michal from behind and incapacitates her with a tranquilizer. He then takes her to Ruby's house. The psychic does her research, and learns that whenever the vessel is sedated, Dolos is also at peace.
The detective wants to put a bullet in her head right now, but Ruby knows he’ll be dead before he pulls the trigger, because the devil is still aware of its surroundings, even though Michal is unconscious. In the end, Ruby concludes that they need to find a new host. Ruby knows that the part of the real Michal who really wants to live her life is still conscious.
Since they need to know what they should do, Ruby leaves a pen and paper beside her and some words of encouragement to keep fighting, hoping to get a response. Lo and behold, Michal starts writing; she says that she has a plan in mind. Her father wanted to become the demon’s vessel long ago, so they should make it happen now.
They won’t have to worry about him as he is going to be euthanized anyway. Ruby knows that it is a risky plan, but it is the only chance they have got. The next morning is David’s final day in this world, and he will be executed in a few hours.
Before that, Michal meets him; she tells him that the demon is asleep right now, and requests that he take the demon with him. David, who loves his daughter a lot, agrees without any hesitation. He is ready to endure the brutal demon for the sake of his daughter’s freedom; the two hold hands and begin the ritual with the help of Ruby.
The scene then cuts to the execution process, where David is strapped to a chair. Ruby and Michal anxiously watch from outside, hoping everything goes well. But just then, it seems like the demon has awakened from his slumber and is already in David’s body.
David makes the doctor who is administering the injection lose control of his body. Despite this, the doctor still manages to administer the lethal injection, leading to David’s death. In the end, Ruby and Michal celebrate that they have finally gotten rid of the demon.
But as the movie comes to an end, we are left wondering if Dolos is still alive when Michal lets out an evil grin.
