Sarah Tyler (Isabella Calthorpe) is traveling back to England after spending some time in Los Angeles. Upon her arrival, she reunites with her stepfather, who is busy with paperwork, and is told to rest for the night. Meanwhile, she takes the opportunity to check on her younger brothers, who are at the nearby barn fixing a jeep. Sarah then heads over to the barn, where she encounters her brothers and their friends enjoying a party amidst a brewing storm.
The party includes Peter Gadiot as Stephen Moore, Gemma Atkinson as Emily, Gabriel Thomson as Charlie Moore, Tom Felton as Gary Ashby, and Joshua Bowman as Doug Walker. Also present in the barn is their youngest brother, Luke Moore (Antony De Liseo), who is peacefully sleeping with their dog, Stoner, among the hay. Sarah wakes Luke and learns that their parents have been arguing over unpaid bills and a suspected affair involving their mother, which shocks her. She sends Luke back to sleep and dismisses Stoner, but the tension unresolved in the household hangs over the night.
As the storm intensifies, Sarah leaves the barn and joins the party, questioning why she was kept out of the loop about her family’s issues. Stephen, visibly upset, reveals that their stepfather accused their mother of having an affair with a man whom she is supposedly paying a large sum of money. Sarah refuses to believe her mother could be unfaithful, doubting the accusations.
Later, a power outage caused by the storm plunges the house into darkness. Upstairs, the group notices blood dripping from the ceiling at the top of the stairs. Gary ventures into the kitchen to find candles but soon separates from the group, only to discover a horrific scene: blood leading from their father's room, which they find empty except for their father's lifeless body. His corpse bears clear signs of a savage attack—rib cage torn open and internal organs missing. In a heartbreaking moment, Gary also finds the collar of their dog, Stoner, and its bloody remains.
Suddenly, the group witnesses a monstrous creature attack from the shadows—a beast that immediately rushes to attack them. They manage to shut the door in time, but the creature relentlessly pounds against it, trying to get inside. When Gary calls out, the beast hears him and switches its focus to him, ripping him apart in a gruesome struggle. The beast then begins to batter the door of the bathroom where Sarah and others have taken refuge. As the horror continues outside, Sarah notices a hidden passageway in the bathroom that leads to the attic. In a desperate attempt to escape, the group climbs through the passage, temporarily saving themselves.
In the attic, they regroup and contemplate their next move. Sarah mentions that her mobile phone is downstairs in her bag, and the others reveal their phones are dead. Stephen has one, but it’s out of battery. Sarah also remembers that Luke is still at the barn. She then notices a telephone in their father’s room, sparking a plan to retrieve it and call for help. Emily spots another passage leading to a different room, which could offer a way out.
While Sarah attempts to distract the monster to give Charlie time to reach the phone, the creature detects her and pursues her outside. Charlie manages to make the call, telling the police about a wild animal loose in the house. Sadly, as Charlie tries to communicate, he is overtaken and killed by the beast. The creature then targets Sarah, biting her leg as she tries to escape back into the attic.
Meanwhile, John Lynch and Officer May are dispatched to investigate the call about the wild animals. McRae [john-lynch] is a trained dog catcher, skeptical at first but determined to assess the situation. When they arrive, they discover evidence that suggests the report is not a hoax—they find an abandoned car with no sign of the driver and a pile of clothes nearby, indicating something sinister has happened.
Back at the house, Luke unknowingly wanders into the chaos and finds the dead body of Gary. The beast, now aware of Luke’s presence, begins to pursue him. Sarah, after falling through the ceiling in a frantic escape, manages to regain her composure and helps Luke and the remaining survivors reach the roof. Both McRae and Officer May arrive, but they too are killed by the creature. Sarah retrieves a handbag—belonging to her mother—and flees toward the barn, where Stephen is attempting to fix the jeep to escape.
As the survivors regroup, tensions escalate. Sarah reveals that her mother’s handbag contained proof that Stephen tampered with his mother’s car to prevent her from seeing her lover, implying Stephen’s potential involvement in the chaos. In a flash of anger, Stephen knocks Sarah out, but she awakens and retaliates, hitting him and causing him to run out into the night, where he is attacked by the beast.
Inside the barn, Sarah begins to transform into a monstrous figure herself. Meanwhile, Luke and Doug Bowman hide under a table as the creature returns. Just as it is about to kill them, Sarah—now the other beast—intervenes, attacking her own monstrous counterpart. Luke escapes, running to the car, while Doug tries to shoot the creature but is eventually bitten and killed by Sarah.
As dawn approaches, Sarah reverts to her human form, revealing that the other creature was actually her mother. In the aftermath, Sarah finds Luke inside the car, and they drive away to seek safety. The film closes with the reveal that Gary, believed to be dead, is actually still alive, hinting at the ongoing threat or the possibility of more horrors lurking just out of sight.
