After she learns that her boyfriend Garrett has been unfaithful, sorority sister Megan, portrayed by Audrina Patridge, decides to get revenge with the help of her friends - including Cassidy, Jessica (Leah Pipes), Ellie, Claire (Jamie Chung), and Chugs. They pull off an elaborate prank by staging Megan's fake death while making out with Garrett. However, the prank takes a dark turn when Garrett, attempting to dispose of what he believes to be Megan's lifeless body in a steel mill, inadvertently kills her with a tire iron after a comment from Jessica about releasing air from her lungs. In a panic, the group decides to hide Megan's body in a mine, leaving the murder a secret.
Fast forward eight months, the girls have drifted apart but the shadow of that fateful night lingers, particularly for Cassidy who grapples with guilt. At a graduation party, they receive a chilling message: a picture showing a robed hand clutching the bloody tire iron used to kill Megan. While suspicion falls on Garrett, Chugs defends him, claiming he's changed since that tragic day. Jessica dismisses the message as a sick joke and the party continues, despite the unease. Megan’s younger sister, Maggie, arrives to honor her sister's memory, adding an emotional layer to the gathering.
As the night progresses, the girls start to experience horrific events. Chugs, unaware of her therapist's recent murder, is killed by a mysterious hooded figure right after leaving for her appointment. In another part of the sorority, Claire and Jessica discuss the incident when another sorority girl named Joanna overhears and is subsequently murdered by the same killer wielding the tire iron. Later, at the big graduation bash, Claire's boyfriend Mickey meets the same fate, leaving Ellie shaken and fearful.
In a desperate quest for answers, the remaining girls receive a threatening text alongside a video captured during Megan's death, instructing them to meet at the steel mine in twenty minutes. In a twist, while on their way to confront Garrett, they find him wounded and also receiving the sinister messages. Ellie theorizes that Megan might not be dead and could be seeking vengeance. To confirm their fears, Cassidy is lowered into the mine shaft, where she discovers a bloodied message reading, "Theta Pi must die."
Back at the sorority house, the atmosphere turns increasingly tense when texts from Chugs' phone lead the girls to believe she's in peril. One by one, they fall victim to the killer until Cassidy and Jessica uncover that Mrs. Crenshaw, their house mother, has died while searching for the assailant. In a frantic race to escape, Cassidy, Jessica, and Maggie navigate the chaos, but when it seems all hope is lost, they are met with betrayal as Andy, Cassidy's boyfriend, reveals himself as the true killer. He confesses it's all part of a twisted plan to have a future with Cassidy, eliminating anyone who knows about Megan's death.
The climactic showdown leads to a battle filled with treachery and desperation as Cassidy attempts to save Maggie from the flames instigated by Andy. After a heroic struggle, Andy is defeated, but not before significant loss occurs. As dawn breaks, Cassidy, Ellie, and Maggie emerge as the only survivors from the horrific night, barely escaping with their lives as the sorority house burns around them.
Fifteen months later, as Theta Pi undergoes renovations, Maggie, now a new member, participates in a celebration. Nevertheless, a mysterious figure with a garden trowel looms in the distance, hinting that the horrors of the past may not be entirely over, as the camera reveals eerie wrist markings suggestive of Garrett’s survival from his supposed suicide attempt. The chilling ending leaves viewers pondering the true implications of their tragic evening.
