Studio 666

The movie opens with a female member of a rock band crawling down a hallway inside a lavish home while begging for her life. She is chased by a man who ultimately catches her and kills her by smashing her head with a hammer. Nearby, another bandmate is already dead, with his face grotesquely split open, hinting at a violent massacre.

The scene shifts to the modern-day, where the Foo Fighters band meets with their manager Shill to discuss their 10th album. Front man Dave Grohl is struggling with a creative block and cannot conceive new songs, while Shill emphasizes the urgency due to financial debts. The band decides to attempt recording outside the studio to spark inspiration.

Shill arranges for the band to rent a mansion through property manager Barb Weems, believing the supernatural atmosphere will inspire new music. Upon arrival, Grohl has psychic visions of the earlier slaughter, which influences him to convince the band to stay and record at the haunted house.

While setting up, a crew member dies in an electrical accident caused by spectral interference. Despite this, Grohl urges the band to continue recording, feeling invigorated by the house's dark energy. Grohl also attempts to create new music, plagiarizing a song in a moment of inspiration, but remains creatively unfulfilled.

Grohl experiences demonic nightmares, followed by a nocturnal walk into the woods where he finds a dead raccoon nailed to a wall and a mysterious tape by the band Dream Widow, who were previously slaughtered. Playing the tape awakens a malevolent spirit that possesses him, marking a turning point in the story.

Grohl, possessed, plays an extraordinary guitar solo, claiming to have invented a new musical key called 'L.' This energizes the band temporarily, and Grohl dismisses the crew so they can focus on recording. Nonetheless, his behavior becomes increasingly unstable and erratic.

Nighttime horrors intensify as Grohl commits multiple murders, including decapitating the delivery guy with hedge clippers and killing band members Rami and Samantha while they are intimate. The band members grow suspicious and frightened, and the house becomes increasingly disorderly and grotesque.

Smear and Mendel find the cursed book underneath the drain with the dead raccoon. They learn about a ritual to exorcise the demon, revealing that the house is atop a portal to Hell. The band prepares to perform a spell to save Grohl and themselves from the demonic possession.

The band completes the exorcism spell, causing Grohl to vomit out the possessed spirit of Dream Widow’s front man. Grohl then physically defeats the demon, freeing himself and finally ending the hellish possession, but not before the spectral remnants are expelled into the underworld.

As the band prepares to leave, they encounter Shill and Weems, who reveal themselves as satanic worshippers responsible for orchestrating the house’s dark history. A struggle ensues, resulting in the deaths of Weems, Shill, and Mendel, while Smear’s head is crushed under a van’s tires.

The surviving band members attempt to escape, but Weems stabs Mendel before dying, and the others are confronted. Shill laughs, revealing that the cursed song has been completed—an epic track designed to save Rock and Roll—signaling that Dave Grohl’s music career is forever changed.

The film jumps to a year later, showing Grohl performing solo in front of an excited crowd. As he prepares to sing the demonic song, his eyes turn black, indicating that he is permanently possessed by the malevolent spirit, hinting at his future dark path.