One year before the Abaddon Hotel was slated for demolition after the disappearance of an investigative team, the property is purchased by Russell Wynn, a wealthy playwright who plans to stage his ominous work Insomnia inside the haunted venue.
An investigative documentary follows the events at the hotel, guided by the Morning Mysteries crew led by Vanessa Shepherd. She accepts Russell’s invitation to record the production process, hoping to pierce the mystery surrounding the place. The crew is shown around by Jeff Stone, Russell’s head of operations, and the atmosphere quickly grows tense as Russell greets and introduces Gregory Sandvick, Max, Jane Maloney, Isabel, and Harvey.
Father Paulis, a local priest hired by Russell, presents Russell with an undisclosed item, and a dare sends Jane into the basement where she witnesses a clown mannequin appear to move on its own. In a later interview, Max reveals that Russell was involved in a near-fatal car accident years before, a detail that seems to illuminate Russell’s unpredictable past. Isabel encounters the ghost of Sara Havel, a Hell House staff member who vanished years earlier, and she decides to quit. Vanessa also senses the supernatural, spotting the ghost of Jessica Fox, another member of the vanished team. Despite Louie’s insistence that they should leave, Vanessa chooses to stay and press on with the project.
Before opening night, the crew heads to a bar, and Russell warns Vanessa and Louie that they shouldn’t come, without fully explaining why. Vanessa pursues him, and Russell whispers something that unsettles her. Later, Vanessa asks Louie to join her in seeking Father Paulis for answers. Paulis drops a stark truth: Russell intends to liquidate his assets to charity after the show. The news shocks the Insomnia crew, and Jeff confronts Russell, while footage shows Russell surveilling the original Hell House team and the subsequent investigative journalists.
During a rehearsal, Andrew Tully interrupts a scene between Max and Gregory, and the lights flicker before Tully fatally strikes Gregory. Panic erupts as cult members infiltrate the hotel and slaughter everyone inside. Vanessa is dragged to the basement by a cult member and knocked unconscious just as a glowing red hole opens. She narrowly avoids sacrifice when Russell intervenes, triggering a collapse of the roof.
The next day, a news report notes that all audience and staff members survived unharmed, but Russell remains missing. Vanessa and Jeff credit Russell’s interference for their survival, while an interview reveals that Russell had legally died for two minutes before being revived. The original Hell House team abruptly returns, trapped inside the empty hotel, where they are greeted by Russell. He explains that he is the one who closed the gateway, and that they—the team—are the ones who opened it. With a quiet resignation, he tells them it’s time to move on before vanishing. The team supports one another, accepting their fate as they face an uncertain future together.
