Novelist Ohm Bauman travels to the secluded Bilberry Woods Hotel in rural Ireland to fulfill the final wishes of his late parents by scattering their ashes across the estate's grounds. Upon checking in, Ohm is unsettled by the hotel’s quiet gloom and the bizarre behavior of the staff: owner Cob, hostile front-desk clerk Mal, bartender Fiona, and peculiar bellhop Alby. Ohm learns that the hotel has a dark local history involving an ancient witch said to haunt the premises, specifically lingering around the sealed honeymoon suite.

That evening, Ohm is plagued by waking nightmares and shadowy apparitions in his room. Exploring the grounds, he meets Jerry, an eccentric man living in a camper outside the hotel who warns Ohm that the hotel's managers lure vulnerable guests into dark ritual entrapment, and mentions how psilocybin mushrooms open mortal minds to the spirit world. When Ohm returns to the hotel, he discovers Alby has left him an unsolicited novel manuscript and that personal artifacts belonging to his parents have mysteriously relocated across his room.

The hauntings escalate violently as the hotel seems to shift layout, trapping Ohm inside. Hallucinations of the "Conquistador"—the ruthless protagonist from his own popular novel series—manifest in the corridors, taunting his insecurities and grief. Investigating a layout map, Ohm realizes the only unsealed emergency exit is located in the deep basement. With the central stairwells and elevators locked, Ohm squeezes into the kitchen dumbwaiter to descend into the hotel's subterranean foundation.

In the labyrinthine basement, Ohm encounters the witch: a gaunt, terrifying entity emerging from the dark. Remembering ancient folklore warnings, Ohm desperately draws a protective circle of chalk on the floorboards around himself, holding the screeching apparition at bay through the night.

In the morning, Mal comes down to the basement expecting to dispose of Ohm, only to find Jerry has breached the hotel to intervene. Panic breaks out as Mal realizes the ancient entity cannot be contained.

Attempting to flee the hotel with stolen guest valuables, Mal sprints toward the elevator, only for the heavy iron gates to slam shut on him. Realizing Ohm possesses the master keys, Mal rushes into the dark basement catacombs with a weapon.

Before Mal can reach Ohm, the witch manifests from the ceiling shadows. In a horrifying display of supernatural retribution, the entity wraps spectral iron chains around Mal’s hands and drags him screaming down into the dark underworld abyss.

Ohm, who had failed to completely close his chalk circle before the struggle, is also ensnared by the entity's chains. Hours later, Ohm awakens on the cold basement floor alone, the hotel quiet. Looking down at his wrists, he discovers deep, purple bruises where the spectral shackles gripped him. Remembering Jerry's words about opened perception, Ohm realizes the veil between the living and the dead has been permanently lifted. Having survived his ordeal and confronted his grief, Ohm leaves the hotel, agreeing to read Alby's manuscript and sitting down to write a hopeful, redemptive conclusion to his own fictional saga.