The film begins with grainy footage depicting a mysterious ritual in which a girl is positioned at the center while a hefty man enters a drawn circle. The scene becomes grim as the girl is hanged, drawing focus to a second girl revived from a state of unconsciousness, revealing a wine-colored birthmark beneath her eye.
Piper (Sora Wong), a blind teenager, attempts to engage with a group of girls at a bus stop in hopes of making friends. However, her stepbrother Andy (Billy Barratt) intervenes, guiding her away from the mockery those girls hurl behind Piper’s back. Their lives take a sudden turn when they are left to live with Andy's father Phil (Stephen Phillips), who ultimately meets a tragic end from a drug overdose in the shower.
Upon meeting Wendy (Sally-Anne Upton), a social worker, plans are made to place Piper in foster care with a woman named Laura (Sally Hawkins). Andy is slated for separate placement, causing him concern as he believes they are meant to remain together. Through a series of discussions, he persuades Wendy to allow both siblings to stay under Laura’s roof.
Once at Laura’s home, they encounter her nephew Oliver (Jonah Wren Phillips), a mute boy who shares a disturbing similarity with the girl from the earlier video, bearing a similar mark under his eye. The siblings reside in a room that once belonged to Laura's late daughter Cathy (Mischa Heywood). Laura exhibits clear favoritism towards Piper and is noticeably cold towards Andy, even mocking him by intentionally misnaming him.
During their father's funeral, Piper inquires how he looks, but Andy responds misleadingly, attempting to spare her feelings. Laura inadvertently reveals the truth about Andy not having looked at Phil, despite Piper insisting on transparency with her phrase "grapefruit", their unique term for honesty. At the funeral, Laura insists Andy stick to customs, encouraging him to kiss Phil’s lips rather than his forehead, which is profoundly unsettling.
The narrative escalates when Laura initiates a night of drinking and dancing with the siblings. Amidst their camaraderie, Laura reveals deep emotional scars left by Cathy's drowning. Meanwhile, Andy expresses to Laura the abusive nature of Phil, recounting how Piper's mother brought him the familial warmth he craved.
As the relationship dynamics turn darker, Laura’s malicious habits emerge. She sets out to deceive Andy into thinking he wet the bed by throwing urine on him while he sleeps. Tension builds further when she bathes Oliver, who begins to show abnormal behavior, displaying bright red eyes.
Andy is additionally haunted by visions of Phil's ghost and when he finally decides to shower, he accidentally injures himself while contemplating his worries about Piper's well-being. As they navigate their eerie new environment, Piper unearths disturbing secrets, including the frozen corpse of Cathy in a shed, unveiling the true horror behind their new guardian.
Manipulation takes its toll as Laura attempts to turn Piper against Andy, leading to violent confrontations. In a desperate reach for help, Andy attempts to alert the authorities, realizing Oliver may not actually be who Laura claims him to be. Amid chaos, he uncovers a series of grotesque behaviors from Oliver, who becomes increasingly destructive.
In a shocking turn, Laura's duplicity reaches deadly levels as she attempts to eliminate Andy and Wendy, leading to a tragic conclusion. When Piper learns the horrifying truth about Laura's actions and discovers Andy’s lifeless body, it triggers a desperate struggle for survival.
The climactic climax sees Piper escaping Laura's grasp during a storm, leading to a suspenseful resolution as she glimpses her brother's enduring love through a comforting message. As the police draw near to uncover the grim realities within Laura's home, they find Oliver, now identifying himself correctly, and reach the macabre scene of Laura with Cathy's remains, closing a tale filled with twisted familial bonds, betrayal, and the fight for survival against sinister forces.