Whilst extracting oil from a site, a worker unexpectedly veers away from his machinery and collapses, with blood streaming from his ears.
In the stunning landscape of the Welsh mountains, a prosperous family—comprising the politician Gwyn, his wife Glenda, and their two adult sons, Guto and Gweirydd—is hosting a dinner soirée at Glenda's ancestral estate. Their guests include Mair, a neighboring farmer who shares a history with Glenda, and Euros, a businessman who has been conducting mineral drilling on the family's land.
To assist in the preparations for the evening, Glenda enlists the help of a young woman named Cadi, who arrives on foot from the nearby village, her hair still damp, and with a tendency to remain silent. As Cadi aids Glenda in the kitchen, she silently observes the family's dynamics. One of the sons, Guto, grappling with drug addiction, suffers a mishap early on when he drops an axe and injures his foot. Meanwhile, Gweirydd, who is in the midst of training for a triathlon, adheres to an intense diet and exercise routine.
Cadi's observations of the family's way of life begin to unsettle her. She is particularly distressed when Gwyn kills a few rabbits, bringing them in for dinner, an event that triggers an emotional response and stains a clean tablecloth with mud when she hears the gunfire. Oddly enough, Gwyn experiences excruciating pain and auditory turmoil whenever he confronts Cadi. In a startling moment, a bottle of wine explodes in Euros's hand as he accuses her of being lazy. Following this, Cadi picks up a shard of glass and seemingly inserts it into her vagina, further illustrating her disturbed mental state.
As the evening progresses, when Guto asks Cadi for drugs to help him navigate the party, she leads him into the woods where they harvest psychoactive mushrooms, which he consumes before returning to the dinner table.
With Mair now present, the dinner party officially commences. She explains that her husband, Iori, has been delayed due to an emergency involving a vehicle submerged in a nearby lake, in which he is assisting with the recovery efforts.
The environment at the gathering is tense and awkward. Mair maintains a polite demeanor but is clearly unsettled by Glenda's conduct. Gweirydd openly questions his father's recent health issues, causing embarrassment for Gwyn in front of the other guests. Guto expresses disdain for Gweirydd's raw-meat diet, leading their parents to order him away from the table. He retreats to his room to mix and inject the leftover mushrooms.
Feeling redundant, Cadi wanders back into the woods and reclines on the grass, blissfully smiling as tendrils of vines and blossoms come alive, illustrating her deep, mystical connection with nature.
As the evening unfolds, the dinner party's ulterior motive is unveiled. Glinda, Gwyn, and Euros are all eager to persuade Mair to permit exploratory drilling and mining on her land, particularly at a location referred to as "the Rise." Mair, however, expresses her dismay, revealing that this spot is thought to be the resting place of a local goddess, a sacred site that the townsfolk avoid for fear of disturbing her. Mair is horrified by their intentions, firmly rejecting their proposal. In response, Glenda accuses her of harboring superstitions.
In a disturbing turn of events, Guto's leg becomes necrotic and infested with maggots. Cadi, taking matters into her own hands, seduces Gweirydd, leading him outside to where Guto lies in agony. Fueled by drugs and delirium, Guto reveals a chilling secret about Gweirydd's departure from the hospital: he had assaulted several comatose female patients. Under Cadi's manipulation, Gweirydd finds himself compelled to amputate Guto's leg with an axe. Their dark encounter soon escalates to a primal act of passion against a tree, with Gweirydd screaming in pain as the hidden shard of glass within Cadi inflicts injury.
Back at the house, Mair receives a phone call that reveals a shocking truth: the car pulled from the lake belonged to Cadi. Horrified, she and Glenda realize that the woman who has been helping them is not the real Cadi but rather the goddess of the Rise, possessing Cadi’s deceased body. In a moment of terror, Mair flees, leaving Glenda to confront her fate.
The goddess reenters the house and enacts vengeance on Gwyn by driving a skewer into his ear.
In a harrowing climax, a severely injured Gweirydd staggers back with the lifeless Guto draped across his shoulders, only to succumb to blood loss shortly thereafter. In a trance-like state, Glenda undertakes a menacing act, dismembering Guto's body and serving his maggot-infested leg to Euros, who devours the leftovers mindlessly. As she then shoves a shotgun barrel in his mouth, she utters, > "After you've taken everything, what will be left?" She pulls the trigger before taking her own life.
Eventually, the goddess returns to her sacred domain, the Rise, and incinerates all the bodies, closing the grim chapter of the evening.
