Based on the book by Jay Anson, which is supposedly based on a true story, the film tells the tale of George and Kathleen Lutz (played by TV actor James Brolin, and Superman co-star Margot Kidder), who have just moved into a new house with their 3 kids and are so thrilled by the low-price they've bought it for, they're totally unconcerned with the fact that one of it's previous occupants went crazy and blasted his entire family with a hunting rifle.
No sooner do they move in though, then all sorts of weird things start happening. Doors and windows slam shut and appear to jam themselves closed. Swarms of flies appear at the back window of one of the rooms, irrespective of the time of year. The occupants hear voices and the local priest (Rod Steiger) visits and suddenly becomes violently ill, after also claiming to hear voices.
Eventually they discover a room behind a walled off area of the basement, which they believe was part of the old building that once stood there, which happened to be an institution for the criminally insane. They then discover an old well under the floorboards, which James Brolin falls neck deep into, before finally abandoning the house during another ghostly attack.
Whilst the movie offers one or two genuine chills, the plot seems to drag along at a snails pace and never really amounts to anything. Just how much of this actually happened in reality has also been greatly disputed by many people over the years, so take any claims of this being true with a huge pinch of salt. All in all, the film is watchable but is relatively dull.