The film begins with Captain Elliott Spencer (Doug Bradley) engaging in an ominous game with the Lament Configuration box, which tragically transports him to Hell, leading to his transformation into the Cenobite known as Pinhead. Fast forward to the present day, where we find Kirsty Cotton (Ashley Laurence), confined in the Channard Institute, a psychiatric facility, where she is being interviewed by Homicide Detective Bronson (Angus MacInnes). During a police investigation of a house associated with her late father, Larry, her stepmother, Julia, and uncle Frank, they discover the blood-soaked mattress where Julia met her end in the previous installment, and it is taken for evidence.
Kirsty encounters Dr. Phillip Channard (Kenneth Cranham) and his assistant Kyle MacRae (William Hope), recounting her harrowing tale. Before she is dismissed, Kirsty implores Bronson to incinerate the mattress, her only hope to resurrect Julia from the depths of Hell. In a private conversation, Channard has other plans with Bronson. During her initial night at the hospital, Kirsty is disturbed by a young girl named Tiffany (Imogen Boorman), who has been institutionalized for months and possesses an exceptional talent for solving puzzles. Plagued by eerie voices, Kirsty uncovers a grim message scrawled on the wall from a skinless figure she believes to be her father: > "I AM IN HELL. HELP ME."
Kirsty confides in Channard about her fears, expressing the possibility that her father might still be alive. In a chilling twist, Channard pilfers the cursed mattress, taking it to his home where he becomes enthralled with the Lament Configuration and the portal it provides to Hell. Kyle, suspecting something sinister, secretly infiltrates Channard's house, where he witnesses the horrifying scene of a masochistic patient being sacrificed on the very mattress that Channard seeks to exploit. Through a grotesque ritual, the skinless Julia emerges, and Channard brings her victims to sustain her, constructing her body piece by piece.
Eventually, Kyle informs Kirsty of Julia’s resurrection and Dr. Channard's obsession, prompting them to confront the doctor together. In a moment of shock, Kyle stumbles upon Julia, and in a horrific turn of events, she captures him, leading to a chilling encounter. Their paths intertwine dramatically, leading to an intense confrontation between Julia and Kirsty as the two attempt to navigate the terror of Channard's schemes.
Amidst the chaos, Tiffany is manipulated to unlock the puzzle box, inadvertently unleashing the Cenobites, including Pinhead, who recognizes the true architect behind the gateway to Hell. Simultaneously, Channard's insatiable thirst for power pulls him deeper into the labyrinth of Hell's horrors, where he faces the fury of Leviathan, the god of Hell. Channard’s relentless ambition ultimately transforms him into a Cenobite, burdened with a new and horrific existence.
Kirsty and Tiffany desperately seek an escape, but are confronted by the malevolent forces that dwell within. In an attempt to free themselves, they light a fire within Frank’s dominion of Hell, which leads to a climactic confrontation with Julia and Frank. A desperate struggle ensues, resulting in Julia betraying Frank, effectively severing ties with her past.
With danger lurking at every corner, Kirsty and Tiffany make a harrowing attempt to flee back to the hospital, only to be hunted down by Channard in his monstrous form as a Cenobite. Ultimately, a fierce struggle takes place, leading to a dramatic conclusion where alliances shift and fates collide. The film reaches a gripping end as an eerie revelation and a haunting question linger in the air, prompting viewers to ponder the nature of pleasure and pain in a world where such entities exist.
