Seventeen-year-old Jenny Ortega is asked to the prom by her crush Jason Briggs. While shopping for a prom dress with her best friends Courtney Rix and Ginger Rain, she sees a teenage girl inside the reflection of the window, wearing what looks like a large sack. Jenny brushes it off and returns home, admiring herself in the mirror of her bedroom inside the dress. She takes a picture, and sees the same pale girl inside the picture. Just as she spots the girl in the picture, her mother's friend Ashley Morono arrives to visit. Shortly after Ashley's arrival, Jenny's best friends arrive as well. The five women watch a horror movie based on the legend of Bloody Mary and decide to do it themselves for fun. They see a girl in the mirror, as if they are watching her walk towards them in a window from a long distance away. The water coming out of the faucet explodes, drenching them. The candles begin to shake, the flames flickering, as well as the lights. As the girl grows nearer, the Cocktailjurken 2013 flickering and shaking grows fiercer. The candles fall from the counter, igniting a circle of fire around them. The girl split voor Prom Dresses grows steadily closer. Ashley collapses onto the ground in tears, flashing back to the first time she had experienced Bloody Mary when she was a little girl with her younger sister Aubrey. Courtney, who is a cheerleader, jumps over the flames and tries to get out of the bathroom, but the door is locked - even though it doesn't have a lock. She begins to sob, banging on the door and trying to pull it open. The sound of nails against wood resonates throughout the room and Courtney collapses, blood running down her face. There are claw marks on it. Jenny turns to the window again and the mirror has spider-webs cracks in it. The girl is now in front of Jenny, inside the fire. She makes a creepy noise, her mouth opening impossibly wide. Suddenly, everything goes away. The candles, flickering steadily, are on the counter again. The water is now running and the water that had previously drenched all of them is now gone. All evidence of the event have disappeared. The door is now unlocked.
When they try to escape the house, they discover the doors and windows are all locked. Lindsay disappears, and in their search, Ashley finds her hanging inside her bedroom, dead, Bloody Mary standing behind her, arms wrapped possessively around her neck. Ashley stumbles down the stairs, shocked. She feels someone watching her, and spins around to the mirror at the last landing. She creeps closer to it, but sees no one. A window beside Courtney explodes when she gets angry and screams, calling Bloody Mary names. She is dragged out of the house by an invisible force and thrown outside into the front yard. No one else is able to leave to help her. Courtney leaves, unwilling to stay with them. On her answering machine at home, she finds numerous phone calls from her boss, Junette, at the strip club where she works to pay for her apartment. It is revealed that she had been kicked out of her home by her parents when she inadvertently caused the death of a fellow student at her school.
She goes back to work, intent on forgetting the night's events. While dancing, she sees Bloody Mary again in the crowd, but then realizes it was just a waitress. She leaves, and as she is walking to the bus stop, she feels that someone is watching her. She turns, but finds no one. When she returns home, a photograph of her and her parents are hanging on her wall, but she thinks she sees Bloody Mary in the image. She gets onto a chair to look into it, and Bloody Mary jumps out at her. She falls off the stool, hitting the ground. When she sits up, her body-length mirror shows a girl in the reflection (Mary), as she is falling down the stairs of Jenny's home. Then, it shows a girl being buried alive inside a blue intricate glass coffin. The girl inside is Bloody Mary. Meanwhile, at Jenny's home, they hear a sound upstairs and then Lindsay's screaming. They race upstairs to find Lindsay's hung body, which Ashley had not told them about. They are unable to enter the room to save her, and Jenny's mother falls down the stairs, breaking an arm. As they try to get to her, iron/metal claws erupt from the walls all over, ultimately cutting open Jenny's leg.
Bloody Mary appears, chasing Jenny. When Jenny trips, Bloody Mary grabs her head, pressing her fingers into Jenny's eyes. Instead of feeling pain, black and white colors flash in front of her eyes and then she collapses. When she gets to her feet, she is alone in the house. She passes a calendar and realizes that it is May, 1992. She hears screaming echoing from the basement of the house and creeps downstairs. She sees a human Bloody Mary being beaten and raped by a man - that man is revealed to be her grandfather. Upstairs, the front door slams and she hears her mother's voice, screaming. Her grandmother starts screaming at her, too. Her mother races downstairs, and takes Mary in her arms. They are blocked from escaping by her grandparents. It is revealed that Mary is Jenny's sister, born just three months before Jenny. It is also revealed that after her grandparents discovered Mary's pregnancy, they adopted Mary, forcing her mother to agree to turn her over to them; the threat was they would murder Mary and frame Clare for it, ultimately sending her to prison.
Clare and Mary race upstairs when the grandfather pulls a gun. The grandmother attacks Clare while the grandfather traps Mary inside her room. The fight ends in Clare being forced out of the house. It is then revealed that Mary is pregnant with her grandfather's baby. The grandfather tries to rape her again, but she fights back. He murders her by throwing her down the stairs, killing her baby inside her stomach. He buries her alive in the ground, as their land is gigantic. The grandfather and grandmother are murdered by Mary's angry spirit, which was driven by her outrageous amount of pain and fury at what has happened to her. Jenny then is back into her own time, and she gets into a heated argument with her mother about what has happened. As their argument finishes, Courtney arrives again and is trapped inside. She replays what happened to her.
Bloody Mary then appears, and before she can do anything to them, Jenny begins to talk to her. She says that she feels horrible about what happened to Mary and then it never should have happened. She also says that it was a long time ago, and that she needs to let go of it. Suddenly, blood appears on the wall, spelling out words. It is an address to a house. Bloody Mary then disappears. Jenny, Ginger and Courtney convince Ashley and Clare to let them go to the house and figure out what it means. They go to the house and discover another piece of writing in blood from Mary. It says, "Run."
A man attacks them, chasing them to a garage a distance from the house. They succeed in knocking him out and hide inside the garage. Soon, he finds them. They escape and go back to the front of the house. He is armed with a shovel. The door is locked, so Jenny wraps her arm in her sweater and punches the window, breaking off all the glass. Courtney and Ginger are the first inside. When the man appears at the end of the house, Jenny escapes inside. Courtney and Ginger are at the top of the stairs before Jenny trips and falls down them. The man is beating at the door with the shovel, breaking it. He breaks inside as Jenny gets to her feet and Courtney runs down to rescue her. She tells her to run, but the man shoves Jenny to the ground. She hits her head on the wall and sinks to the ground, not moving.
Courtney tries to run back up the stairs when Jenny tells her to, but the man reaches into the banister and grabs her around the waist, pulling her off the stairs and to the ground. Ginger tackles the man from the stairs. Her and Courtney escape up the stairs, provoking the man into chasing them instead of Jenny, who has just gotten to her feet. Bloody Mary appears, writing on the wall in blood, "He killed me." When Jenny says that she thought their grandfather had killed her, she replies, "He did. But he helped." Jenny asks why she has tried to hurt them, and Mary replies, "I was angry at our mother. I was angry at everyone involved with her. I was wrong." Jenny asks how she can help put her spirit at rest. She says that it can only be done by finding her grave and her body and drawing attention to what their grandparents are really like and getting the other man punished.
Upstairs, Ginger and Courtney are hiding inside a closet. The man finds them and breaks into the closet, nearly killing them. They escape out the window after taking him on a wild goose Sexy Trouwjurken chase and circling back to the bedroom, where they climb out the window and onto the roof. The man pops out from a window in front of them, startling them. They nearly fall off the roof. He swings the shovel, slicing open Courtney's arm. Ginger claws at the man's face, cutting open his cheek. Outraged, he punches her, and she collapses but doesn't fall off the roof. The man backhands Courtney and she falls through the roof because of the rotten boards that made the roof.
Jenny creeps out of the house, trying to find the grave. The man finds her and is going to kill her, but Mary appears behind him and screams at the top of her lungs like a banshee. The man releases her, the scream hurting his ears. Jenny seizes the chance, taking the shovel and cutting off the man's head. She finds Courtney kneeling next to Ginger, who is unconscious. Jenny tells her that in order to put Mary's spirit at rest, they must find her grave. They search for it, and end up finding it located near the garage. Jenny breaks it open to see if it is in fact Mary. It is. They call the police.
The police don't believe their story, and they have no evidence that points to the truth of their story. After being questioned once more, they are forced into the police car and are driven to a mental institute. Ginger is the first to be taken, being dragged into the building. Courtney is taken next. Jenny escapes the arms of the policeman trying to take her, but is tackled and given a shot to knock her out. When Jenny wakes up, she is in a hospital bed inside the hospital. She is secured to the bed and begins to freak out. A nurse enters, trying to give her another shot. She resists, but guards succeed in helping the nurse give her the shot. Courtney awakens in a duplicate room and the nurse enters to give her a shot when she starts to scream. She is also bound to the bed. She sees Ashley being dragged kicking and screaming to another room. The nurse gives her a shot, as well.
Ginger awakens in the exact same situation, but when the nurse nears her to give her the shot, Ginger threatens to bite her. She waits until the needle is about ten inches to her arm and leans forward and bites the woman's hand, drawing blood. The nurse still manages to give her the shot. Ashley awakens in the same predicament, but finds that everyone else in the hospital besides her, Jenny, Ginger, and Courtney have been brutally murdered. The doorway to her room was left open and the place is silent, a dead nurse in the doorway.
Bloody Mary attacks her again, but she escapes the room and searches to find Ginger, Courtney and Jenny. She finds Courtney and Ginger inside Courtney's room. Ginger pulls a knife and brutally kills Courtney. Ginger then morphs into Bloody Mary and back to Ginger again. When Ashley asks what happened, Ginger reveals that the man had chanted a spell under his breath on the roof when she, Courtney, and Jenny were trying to survive. It was a chant that only she could hear, and it put Mary's spirit (from when it was enraged and murderous) inside of her. Ginger chases Ashley, morphing into Mary constantly. Jenny escapes her bonds, as well, to find Courtney's dead body. She runs into Ashley and Ashley reveals what had happened.
The two are chased up onto the roof, where Jenny is killed by Ginger. Ginger then disappears, but reappears behind Ashley when she is sitting, shaken, on the roof. Ginger, now Mary, pulls her off the roof. However, Ashley survives when she grabs onto the ledge of the roof. Using her enormous upper strength, she pulls herself back onto the roof and attacks Ginger, who has now returned to her true form. However, Ginger/Mary disappears. Ashley then realizes where she went and goes there after stopping at her house and getting new clothes. She goes to the house to finish off Mary once and for all. There, Ginger/Mary attacks her. The battle ends in Ashley setting fire to the house. Her boyfriend appears out of the middle of nowhere. Ginger/Mary kills him and then attacks Ashley. In order to avenge her friends' deaths and to finish off Mary, Ashley takes her boyfriends lighter, and, just as Ginger/Mary is about to kill her, sets fire to the house.
