The film begins with Jenke's execution by electric chair. However, instead of dying, Jenke's spirit, which has made a deal with the devil, is released and returns to torment McCarthy and his family in their new home. Jenke, now a malicious supernatural entity, seeks revenge and aims to drive McCarthy insane and frame him for his own continuing murders. @ +1
McCarthy starts experiencing terrifying hallucinations, blurring the line between reality and nightmare. His family becomes concerned by his erratic behavior, and a parapsychologist, Peter Campbell, is called in to help. Campbell believes the only way to stop Max for good is to destroy his spirit. © +1
As Max's spiritual attacks intensify, members of McCarthy's family and those close to them are killed in gruesome ways, often with McCarthy himself being framed or made to look responsible. Max's malevolent presence is particularly strong in the house's basement, near the furnace.
The climax involves McCarthy confronting Max's spirit, attempting to send him back to the electric chair to finally destroy him. The film features grotesque special effects and leans into a more traditional, dark supernatural horror style, distinguishing it from the earlier, more comedic House installments.