In 2011, University students Janet and Marilyn are getting ready for Fresher's Week at Uni. It's their first night out as independent 18 year olds without their parents telling them what to do. They go to one of the dorms which is already filled with other Uni students. One boy comes over and hands them both a drink with the rest of the party-goers chanting 'CHUG CHUG CHUG!' As the night goes on, Marilyn & Janet become more and more vulnerable, drinking and doing drugs.
After completing different tasks set by the older years, their last task to play a prank on one of the 'Fresher's'; a boy named Fred who is sitting alone watching everyone else drink. They take him to a closet where he is then blindfolded. Not knowing what they're doing, Fred can feel himself gasping for air. Fred is left calling out to whoever has wrapped him up, unable to unlock the closet door. His brother is also calling out to the pranksters. Not knowing who, or how many there are.
As Marilyn & Janet are getting reading to go to bed that night, there's a power cut all over the university. Janet still feels bad about playing the prank on Fred however, she believes that he'll be okay. As Marilyn & Janet drift off to sleep, Janet hears a loud bang in her dorm. With a flashlight being her only source of light, Janet walks outside, into the corridor hoping to find what made that loud noise. Unable to find a source, she returns back to her room. She then sees Marilyn lying with the covers, covering her head. As she pulls the covers down, she sees Marilyn’s face smeared in blood with the word ‘MURDERER’ written on her forehead. At first, Janet is confused by this allegation however, she remembers the prank she had played only a few hours ago. Automatically knowing that her friend is dead, she drops the torch, attempting to find anyone that can help her. A mysterious figure appears behind her, close behind.
News about the murders has spread across London over the past few days with other Londoners believing that it's 'just another Fresher's prank'. Christina Loomis (usually known as Chris) has just been accepted at the University of Woodsboro after asking to be transferred. Chris is a beautiful 18 year old who holds a dark secret that no one knows. Her secret haunts her every day. She too had carried out a sick prank a week before at her previous University. On that fateful night, she had been giving her best friend drinks (leading her to believe that it was 'just Coca Cola'. The morning after, her friend had died from alcohol poisoning. No one else knows but her. By receiving word that the killer is still on the loose, Chris asks the registration office if she can transfer to another room after discovering that the two girls were killed in her dorm; room 13.
Later that night, she's starts unpacking her suitcase when she hears a knock on the door. A young boy named Charlie is standing at her door. When she opens the door, they start a conversation about the University. Being hospitable, he asks her if she wants to take a tour on campus. After agreeing, they walk along side by side talking about University life. After talking for some time, they come to a halt in the dorm 'common' room. Charlie tells Chris how a boy named Fred had died a while ago in 'this very room'; someone had played a prank and locked him away. Chris then starts reminiscing about her previous Uni and what had happened. Charlie seems upset by their conversation so, goes off to compose himself. When Charlie comes back, he tells her that the boy who had died was actually his brother. He then asks her if she knows what happened in her room a few days ago. Not knowing what he's talking about, she asks him to explain. After telling her what had happened, she reluctantly tells him that she wants to leave to go back to her room and rest. Charlie goes back to his dorm across the campus.
After going back to her dorm, Chris tries to go to sleep however, she keeps on seeing images of Charlie's brother being 'buried' somewhere in the University. However, the next image she sees is the dead carcass' face level to hers. As she drifts in and out of sleep, she hears someone whispering in her ear saying 'I know what you did.' Thinking it's Charlie she tells him to go away however, she's stunned when the mysterious person reveals that it's not Charlie. Jumping at the sound of this figure's voice, she tries to run out of her room into the dorm common room. As the mysterious figure continues to follow her, she finds a small closet in the common room. Trying hard not to blow her cover, Chris peaks through the keyhole to see if the killer is near. She finds a box of matches on the closet floor. As she ignites one of the matches, she nudges something, a life-size doll-like person that's staring at her. The person then mouthes out the word 'SURPRISE'. She screams out in terror and runs out of the cupboard with the wrapped up person close behind her. Just as she thinks she can escape, another wrapped up figure is running towards Chris in the other direction. With the two stopping right near her, Chris asks [during deep and heavy breaths] who they are. They both unravel their cloth to reveal that they're actually Charlie and his brother Fred. Chris then learns that Charlie had faked the death to scare the rest of the University and helped his brother to get revenge on whoever had: decided on the prank, who to play the prank on and who carried out the prank. Another detail was added on before he attempted to kill Chris; he would kill whoever played a prank that turned horribly wrong. With Chris questioning why they played the sick joke, they say that they wanted the rest of the University (and perhaps the rest of the country) that you shouldn't mess around. Charlie then goes onto say that he hates secrets. He then stabs Fred in the stomach. As Fred falls to the ground, Chris tries to run from Charlie however, he stops her in his tracks. He tells her how he killed Janet and Marilyn and he plans on killing her so he could be the only survivor in the massacre. Charlie, using the knife he had used to stab Fred then tackles Chris to the ground, pointing the knife at her heart. As she struggles to set herself free from his grip, she punches him. As Charlie drops the knife, holding his nose, she grabs the knife and climbs on top of Charlie. She stabs him in the chest.
Chris is seen lying on the floor with the knife in her hand, in between Fred and Charlie as the police arrive on campus.
Chris is then left sitting in a white room; wearing an orange jumpsuit; looking at the camera.
