A lonely woman befriends a group of teenagers and decides to let them party at her house. Just when the kids think their luck couldn’t get any better, things start happening that make them question the intention of their host.
Maggie Thompson and her mom Erica move to Erica’s old hometown after she splits from her husband. Maggie befriends teens Andy, Haley, Chaz, and Darrell, and they meet a lonely vet technician named Sue Ann Ellington to convince her to get them alcohol. She only agrees after seeing that Andy is driving a van belonging to his father’s company. Sue Ann then invites the teens and their friends to go to her house to drink safely, but she starts to get too close into their lives at school, which starts to bother them.
Sue Ann’s backstory is that she went to high school with Erica, Andy’s father Ben, and Ben’s girlfriend Mercedes. She had a crush on Ben, which he knew about, and he pretended to be friendly with her, only to set up a prank for her to give a blowjob to a guy she thought was Ben, humiliating her in front of the whole school. She has since gone increasingly unhinged, and even has a daughter named Genie that she keeps upstairs and makes her think she is ill. In the present, Sue Ann runs Mercedes over before going to kill her boss Dr. Brooks and to steal drugs from her job. She later lures Ben to her house and kills him.
Sue Ann invites the teens over for a party before drugging them and tying them up for her own sick plans. An officer goes to investigate, but Sue Ann kills him and forces Genie to help carry him in. Genie turns on her mom and tries to knock her out to save the teens. Erica comes to free her daughter and her friends, but Sue Ann plans to keep Genie there. Maggie stabs Sue Ann and saves Genie. Sue Ann knows she is either going to die or be arrested, so she goes upstairs and lies next to Ben’s body as a fire spreads through her house.
The film starts with Maggie Thompson (Diana Silvers) moving with her mother Erica (Juliette Lewis) and their dog Louie to Erica’s old hometown in Ohio after her marriage falls apart. Erica starts working at a casino and befriends her coworker Stu (Dominic Burgess), while Maggie starts attending a new high school. On her first day, she sees a wheelchair-bound girl named Genie (Tanyell Waivers) and helps give her a push when her chair gets stuck.
Maggie is approached by fellow students Haley (McKaley Miller), her boyfriend Chaz (Gianni Paolo), Darrell (Dante Brown), and Andy (Corey Fogelmanis), who invite her to join them for a party. Maggie tells Haley she is going to a music festival with her mom, but Haley leaves Maggie her number in case she changes her mind. It is also apparent that Maggie and Andy are attracted to each other. On the day of the festival, Erica has to work a double shift, so Maggie decides to join the other teens. When they pick her up, they tell her the party was canceled, so they are going to find someone to buy them booze and they can drink by a rock pile where all the kids go to party.
The teens go to the liquor store and have unsuccessful attempts at convincing adults to help them out. Maggie goes up and sees a woman, Sue Ann Ellington (Octavia Spencer), walking a three-legged dog. She approaches Sue Ann for help, but she declines until she sees the van that Andy is driving has a “Hawkins” logo on it, which is from the company Andy’s father runs. Sue Ann decides to help and goes to buy drinks for the teens. She later goes to her job as a vet technician where she calls Andy’s father Ben (Luke Evans) as he is receiving a blowjob from his girlfriend Mercedes (Missi Pyle). Sue Ann tells Ben that his son is drinking, just before she gets chewed out by her boss, Dr. Brooks (Allison Janney).
Cops show up at the rock pile later that night where the teens are drinking. The lead officer approaches Andy and says he played football in high school with his dad, who was a dick, so he is giving them a ten minute headstart to get out of there.
The teens later meet Sue Ann again for help with booze, and she invites them to follow her back to her house so that they can have a safe place to drink. Although hesitant, the teens agree and follow her there. She guides them to her basement, which is the only place they are allowed to go to. They even start referring to Sue Ann as “Ma.” Chaz makes suggestions to get a beer pong table, among other things, to make the place cooler. When he gets in Sue Ann’s face about it, she draws a gun and makes him strip naked before laughing and revealing the gun doesn’t even work. The teens laugh it off and continue to drink. When Maggie gets home, Erica shows concern over her whereabouts and the fact that she smells like weed.
The next day, the teens find that Sue Ann left a box of booze next to Andy’s van, and even sent them video messages on their phones (Haley gave her their numbers when she was drunk). Sue Ann watches from a distance. She then goes to the casino where Erica works and sees her serving drinks at a table, but a drunk Mercedes takes a champagne glass before recognizing Erica from high school. Ben is with her and also says hi to Erica before they get kicked out due to Mercedes’ behavior. As Sue Ann watches, we see a flashback of her in high school where she was friends with Erica and was invited by Ben to go drink at the rock pile. While there, Ben pretended to be friendly with Sue Ann, who had an obvious crush on him.
Other teens from the neighborhood start to show up at Sue Ann’s basement to party. A thumping sound is heard from upstairs, and Sue Ann claims it’s a busted ice machine that she goes to check out. Haley has to use the bathroom, but the one in the basement is being occupied (for sex), so she breaks Sue Ann’s rule and goes upstairs with Maggie. While Maggie stands outside the bathroom, she hears Sue Ann angrily talking to someone about making themselves heard. Maggie tries to get Haley out of there, but Sue Ann catches them and forcefully pushes them against the wall. The girls get the guys and leave.
In the morning, Maggie wakes up to multiple apologetic texts from Sue Ann. Haley says she’s gotten them too. Sue Ann manages to corner all the teens at school and attempts to invite them to hang out, but they all uncomfortably decline. Haley even tells Sue Ann she needs to find a man and to stop harassing them for attention, which pisses off Sue Ann. Later, she attempts to get another group of teens to go to her place, but they toss a beer can at her car and mock her.
At school, Andy asks Maggie out, and she accepts. They later go to Ma’s house for a birthday party for their friend Stephanie (Margaret Fegan). Sue Ann suggests to Maggie that Andy is going to try and use her for sex, but she ignores her and goes to make out with Andy. Sue Ann approaches them with shots, and Maggie reluctantly takes them per Stephanie’s request. Maggie starts to feel dizzy and passes out. She wakes up the next morning in her bed with no memory of getting back home. She also has bruises on her knees and is missing her earrings.
The teens block Sue Ann from social media, but Haley makes the mistake of sending a video message to all of her contacts, including Sue Ann. She gets a new number and continues to send messages to the teens, going from playful to angry, and then to a tearful plea to get them all to meet her at the rock pile. The teens show up and find Sue Ann there, where she tells them she is sorry for her behavior, and that she has pancreatic cancer. The guys feel sympathy toward her, but Haley notices Sue Ann is wearing Stephanie’s bracelet. She points this out to Maggie and they both note that their own jewelry is missing.
Maggie and Haley sneak into Sue Ann’s house and go upstairs to find their jewelry. They go into her bedroom and find numerous pictures of them, as well as her yearbook with pictures of Erica and Ben out in the open. The girls are then startled by Genie, who is not only revealed to be able to walk, but she is also Sue Ann’s daughter. Genie says her mom has been keeping her out of school and telling her she is too sick to go out. Sue Ann arrives at home, and Genie gives the girls time to escape. When Sue Ann goes to Genie’s room, she gives her a sedative and denies her requests to go back to school. Maggie later sees Andy and tells her she doesn’t want to go to Sue Ann’s house anymore, and that she doesn’t want him there either.
At work, Sue Ann is met by Ben, who invites her out to grab food. When he does meet with her, he tells her that he put a tracking device in the van that Andy drives, and he questions her as to why he has been going to her house. Ben thinks that Sue Ann is trying to get back at him, and he coldly tells her that she has always been a loser. Another flashback reveals that the young Sue Ann was invited to the janitor’s closet by Ben, where she seemingly gave him a blowjob. It turned out to be a prank orchestrated by Ben, and she was actually going down on another boy. All of her classmates saw and laughed at her, leaving her utterly humiliated. In the present, Sue Anna angrily drives home, but she sees Mercedes out for a jog and smashes into her. She then goes to her job to steal a tranquilizer, and she has also killed Dr. Brooks.
Later, Maggie goes home to see Sue Ann is visiting Erica after running into her at the casino, appearing as an old friend, but Maggie is clearly bothered. Even more later, Maggie hears something wrong with Louie and finds him in the shed where his paw is bleeding. She looks toward the woods with her flashlight and catches a glimpse of Sue Ann walking away. When Erica suggests calling Sue Ann for help with Louie, Maggie reveals that she knows Sue Ann and has been going to her house to drink. Erica is furious and she grounds her daughter before going to the liquor store where she confronts Sue Ann about giving minors alcohol, and threatens to call the police if she goes near them again.
Ben later goes to Sue Ann’s house after she removes the tracker from Andy’s van. She tranquilizes him and ties him up to her bed nude. She calls him a dog for what he did to her, so she pumps a bag of Louie’s blood into his body before slitting his other wrist and leaving him to die.
Maggie gets a video message from Sue Ann where she sees her friends there for a party, as well as seeing Sue Ann wear Maggie’s earrings. While Erica sleeps, Maggie takes her car and drives to Ma’s. All of her friends are there, as well as a religious girl named Ashley (Heather Marie Pate) that pretends to be passed out so she won’t feel guilty or get in trouble going home. Andy justifies his being there for Chaz’s birthday, but Maggie tries to get her friends to leave. They are all drugged up off the sedative that Sue Ann spiked their drinks with, and they start to pass out. Maggie runs upstairs to look for Genie, but she finds Ben’s corpse before Sue Ann tranquilizes her as well.
Maggie wakes up in the basement where she and all her friends are tied up by their necks with collars. Everyone else is passed out except for Ashley, but Maggie tells her to pretend to stay knocked out. Sue Ann comes down and takes the teens’ unconscious bodies to do things with them. She presses a hot iron against Chaz’s abs, before sewing Haley’s mouth shut and painting Darrell’s face white. Andy wakes up and tries to help Maggie by pretending to be interested in Sue Ann. They kiss, but Sue Ann sees through the ruse and stabs Andy in his side. Ashley freaks out and tries to run, but Sue Ann whacks her over the head and presumably kills her. Upstairs, a police officer (Tate Taylor) arrives to investigate since there are multiple cars and beer cans outside on her lawn. Maggie tries to make noise to get his attention, but the officer sees Genie and thinks it was her. As he leaves, Maggie cries out, but as the officer turns around, he is shot dead by Sue Ann, who then forces Genie to drag his body inside. She returns downstairs and forces Maggie to take a yearbook picture of her with the unconscious teens. She then tries to hang Maggie until Genie cries out and says the officer is still moving. This is just a trick, as Genie hits her mom over the head with a pan, causing her to fall and start a fire. Genie frees Maggie before helping the other teens free. They try to escape, but Sue Ann has locked the basement door shut. They are saved as Erica noticed Maggie was missing and called Stu to help find her, and they free the teens from the basement. They carry Andy outside, but Maggie and Erica try to save Genie as Sue Ann is dragging her away. Sue Ann calls them both weak, still holding her humiliation against Erica for not defending her. She apologizes for it, but Sue Ann doesn’t care. Maggie then grabs a knife and stabs Sue Ann in her side to save Genie, and they all flee as the flames start to spread.
Sue Ann walks upstairs and sees everyone outside. She continues to go up and walks into the room with Ben’s body. Accepting her fate, she lies next to him and lets the flames consume them both.