In this thrilling and supernatural horror movie, we begin with a gripping scene where a female member of a rock band, Jenny Ortega, runs desperately down a luxurious hallway in a grand mansion, begging for her life as a sinister figure chases after her. The tension escalates as she looks to her side and witnesses another bandmate, whose face has been gruesomely split open, lying lifeless on the floor. The pursuer catches up and brutally bashes the rocker's head with a hammer, leaving viewers with a chilling first image that sets the tone for the story.
Jumping forward in time, the narrative centers around the famous rock band, the Foo Fighters, who are seeking a creative breakthrough. Their front man, Dave Grohl, is suffering from a severe case of writer's block and struggles to come up with new material. Their manager, Shill, played by Jeff Garlin, is impatient and focused on making the band produce a new album quickly to settle their debts. Unlike many typical approaches, Dave proposes trying something unconventional by recording in a different environment rather than a typical studio. As a solution, Shill contacts a property manager, Barb Weems, to find a suitable house that might inspire new music.
The band, including Dave Grohl, guitarists Chris “Shiff” Shiflett, Pat Smear, bassist Nate Mendel, keyboardist Rami Jaffee, and drummer Taylor Hawkins, arrives at an impressive mansion. Their initial tour is welcoming, but Dave (played by himself) begins to experience strange, supernatural visions of violence that connect to the house’s dark history. The mansion, full of ominous atmosphere, seems to influence Dave deeply, and he becomes convinced that staying there is essential for their creative spark. Despite the supernatural signs, the band soldiers on, setting up their recording equipment, but tragedy strikes early when a crew member dies in an electrical accident caused by an unseen spectral entity. Still, driven by Dave's obsession, they decide to continue, honoring the fallen crew member.
The band's struggle with inspiration continues as Dave attempts to rip off an idea from Lionel Richie, symbolizing his desperation. They also meet their neighbor, Samantha, played by Whitney Cummings, who shows interest in befriending them. As nights go by, Dave is plagued by nightmares involving demons and is led to a dilapidated basement. There, he discovers a dead raccoon nailed above a drain and finds an old recording from a band called Dream Widow, who had previously inhabited the house. Listening to the tape, Dave begins to channel the music and even claims to have invented a new musical key, the "key of L." His newfound confidence turns eerie when he is possessed after the recording plays backward, and he begins manifesting hostile, supernatural behavior.
Over the next days, Dave's behavior grows more erratic, and he astonishingly plays an incredible guitar solo during rehearsal, claiming it to be in this mysterious new key. The band, though unsettled, continues to record, but their progress is marred by increasing chaos and violence. Samantha warns them of the house's dark past; she explains that the mansion is built atop a portal between Earth and Hell, cursed by a demon-infested band, Dream Widow, who once used a cursed blood ritual to summon demons to enhance their music. This ritual resulted in the demonic possession of their front man, who slaughtered his band and then himself to prevent a hellish song from being completed.
As the demonic influence takes hold of Dave Grohl, he begins a rampage, killing band members one by one—chainsawing Rami and Samantha during an intimate moment, slaughtering Pat Smear by setting him on fire at the grill, and smashing Nate Mendel with a cymbal. He also consumes parts of their bodies, driven by the demonic hunger. The remaining band members discover the cursed book, hidden beneath the drained raccoon carcass, which contains an exorcism spell needed to banish the demon. Inside, they find a way to save themselves, fighting to complete the ritual despite the demon's wrath.
In a desperate struggle, the remaining members manage to perform the exorcism, which expels the demon's spirit from Dave. As the spirit of the Dream Widow's front man is cast into Hell, the band hopes to escape the cursed mansion. However, evil surprises them—Shill and the property manager, Barb Weems, reveal themselves as satanic worshippers responsible for the house’s dark history. A violent confrontation ensues, resulting in the deaths of Weems, Shill, and the band members. Smear's head is crushed under the van, and Mendel is stabbed by Weems, who is then fatally struck by the vehicle. Dave nearly kills Shill but chooses to stop, recognizing the dark power of the completed song and its potential to change rock music forever.
The story jumps ahead a year, showcasing Dave Grohl performing at a solo concert amidst an enthusiastic crowd chanting his name. As he prepares to perform the final, demonic song, his eyes suddenly turn black, indicating that he has become permanently possessed by the demonic entity he unwittingly unleashed. The film concludes with this ominous note, suggesting that the evil influence now resides within him, permanently transforming him and the future of his music.
Throughout the film, themes of creative desperation, the power of dark forces, and the destructive influence of obsession are explored deeply, creating a dark but compelling narrative about the peril of seeking inspiration at any cost.
