Indie singer-songwriter Grey Kessler, portrayed by Lauren Beatty, grapples with intense anxiety following the success of her debut album and feels an overwhelming pressure to create an equally impactful follow-up. In an effort to curb her bizarre and recurring dreams of herself as a wolf, she turns to medication, though her doctor is unable to identify any physical ailments that might be causing her distress.
Amidst this turmoil, Vaughn Daniels, portrayed by Greg Bryk, a reclusive music producer and former boy-band sensation from the '90s, invites Grey to his secluded mansion to work on her second album. Grey's partner, Charlie, played by Katharine King So, soon uncovers Vaughn's troubling history; he once stood trial, albeit without conviction, for the murder of a singer named Greta. Despite her reservations, Grey accepts Vaughn's invitation, with Charlie choosing to accompany her for support.
As Grey immerses herself in the creative process, her obsession begins to spiral out of control, causing her to dismiss Charlie's worries. Vaughn relentlessly urges Grey to tap into her darkest impulses to fuel her songwriting, shunning Grey's vegetarian lifestyle and introducing her to absinthe. He even pressures her to finish a song that was started by his late wife, who tragically died by suicide. As Grey begins to indulge in her cravings for meat, she descends deeper into chaos, yet paradoxically, her artistic capabilities flourish. Charlie, recognizing the troubling transformation overtaking Grey, insists they leave, but Grey rejects the notion, resulting in Charlie departing alone.
Unexpectedly, Grey discovers that she is becoming a werewolf. A pivotal confrontation with Vaughn reveals that he, too, is a werewolf, and astonishingly, Grey is his daughter. It comes to light that Vaughn was left unaware of her existence, having been misled by her mother, Greta, who claimed that their child had perished while Vaughn was away with his band.
In a dramatic turn of events, Charlie attempts to rescue Grey but finds herself stranded in a snowstorm. As Grey completes her album, she informs Vaughn of her decision to leave, declaring her determination not to follow in his footsteps. In a ruthless attempt to keep her from escaping, Vaughn sends his housekeeper, Vera, and locks Grey in the studio to facilitate her transformation. After blacking out and awakening covered in blood, Grey discovers Charlie lying dead on the road.
Returning to confront Vaughn, Grey aims a gun at him, accusing him of Charlie's murder. Vaughn enlightens her with the painful truth; it was she who unwittingly killed Charlie. In a moment of shared revelation, Vaughn introduces Grey to the complexities of their world, beginning to transform into a werewolf himself. In a climactic resolution, Grey, caught between horror and acceptance, kills Vaughn.
The narrative loops back to Grey's doctor's office, where he closes her file, suggesting she may have been hallucinating throughout her ordeal. Later, Grey finds herself performing her song "Bloodthirsty" on stage to an empty audience, plagued by memories or fantasies of leaving the mansion, stained and bloodied from the confrontation with Vaughn.
