The Hagstone Demon

Douglas becomes the prime suspect because Detective Willis finds him at the scene of Mrs. Brennan's murdered body and knows about his confrontational interactions with Karna. Willis also learns that Douglas has a motive, the building manager job he was given could be tied to the murders, and the detective plans to exhume Douglas's wife Julie's grave, implying he suspects Douglas of involvement in her death as well.

Earlier, Mrs. Brennan had publicly accused Karna of the killings, and Douglas had defended her, making his allegiance suspicious.

Karna is a demon specifically a succubus who preys on vulnerable men. She uses her seduction to lure Douglas into a demonic world, drug him, and involve him in a satanic ritual that culminates in human sacrifice. Her true demonic nature is revealed when she transforms into a fully demonized version during the final confrontation.

Douglas witnesses Karna meeting a pale, sinister man in an alley, raising early questions about her unusual nature.

Julie's ghost appears because her body was secretly buried in the Hagstone's sub-basement, where demonic forces used it as a vessel for evil. The demons are using Julie's spectral presence to torment Douglas, and her re-animated corpse escapes during the climax, killing Carl in the process. Her lingering malevolent presence at the end suggests the demonic plan extends beyond the immediate story.

Julie Elizabeth Elmore's ghost materializes the very first night Douglas arrives, establishing her connection to the building.

Douglas, Barbara, and Carl travel to the cemetery to stop Detective Willis from exhuming Julie's grave, believing demonic forces are using the police to retrieve her body for a supernatural purpose. They find Willis already murdered at Julie's grave, confirming the supernatural intervention and raising the stakes significantly.

Willis had earlier hinted to Douglas about his plan to dig up Julie's grave and reopen her suicide case.

The exact killer is left ambiguous, but the context strongly implies Julie's re-animated corpse or demonic forces associated with her body killed Willis at her grave. The demons needed to prevent the exhumation, and Willis's murder occurs exactly where Julie's body is hidden, suggesting the supernatural entities protecting the buried corpse took action.

The trio realizes demonic forces are using the police to exhume Julie's body for unholy purposes.

Mr. Thompson is actually an incubus, the demonic male counterpart to Karna's succubus. He initially demands that Karna be removed from the basement, seemingly as a landlord, but this is revealed to be part of the demonic hierarchy, the demons work together to orchestrate the building's evil. During the final confrontation, Mr. Thompson appears in fully demonized form alongside Karna.

Mr. Thompson's demand to remove Karna and her cat Victoria seems unusually forceful for a simple building manager.

Karna drugs Douglas with a spiked drink and carries him to a bizarre satanic sex ritual that culminates in human sacrifice. This ritual appears to be part of the demons' larger plan to use Julie's buried body for unholy purposes. The ritual represents the culmination of the supernatural conspiracy happening within The Hagstone.

Karna's request for Douglas to repair something in her apartment foreshadows the intimate and dangerous entanglements to come.

Carl is killed by Julie's re-animated corpse when Douglas discovers her buried body in the Hagstone's sub-basement. The corpse re-animates, overpowers Douglas, escapes from the basement, and kills Carl during the chaos. This tragic death occurs as the supernatural threat reaches its peak.

The trio travels to the cemetery knowing Julie's body holds a dark, supernatural purpose.

Victoria is Karna's hairless cat who becomes a demonic creature in the final act. During the showdown in the boiler room, Douglas, Barbara, and Carl must battle the monstrous transformed Victoria, the last of the demonic forces. The cat's transformation exemplifies how the demonic presence has infected every aspect of the building.

Mr. Thompson specifically mentions Victoria when demanding Karna's removal, emphasizing the cat's importance.

The ending is deliberately bleak: while Douglas, Barbara, and Carl defeat the immediate demonic threat, Carl is dead, the building is abandoned, and Julie's apparition remains watching with cold calculation, contemplating her next victim. This lingering presence implies the cycle of evil is not truly broken and new victims will follow.

The unresolved doom is established from the start, as Julie's ghost appears on Douglas's first night.