How did the ghost acquire almost omnipotent powers?

This is haunted house horror in the tradition of "The Legend of Hell House" (1973), "The Evil" (1978) and "The Amityville Horror" (1979). While it's not as good as "Amityville Horror," it's pretty much on par with "Legend of Hell House" and “The Evil” and would influence future ghostly flicks, like "The Ring" (2002).

The writer of the book and co-scripter, Russell Hunter, claimed the story is based on his experiences while living in the Henry Treat Rogers mansion in the Cheesman Park neighborhood of Denver in the late ’60s.

For me, the apparition is accorded too much power by the scriptwriters in the second half and this provokes a “Yeah, right” response rather than scares or awes. A good example is setting a house on fire at will will. Why Sure! How exactly is a spiritual being able to do this?

Trish Van Devere, by the way, was George C. Scott’s wife from 1972 until his passing in 1999.