George Lutz (James Brolin), his wife Kathy (Margot Kidder) and three stepchildren move into a beautiful house in Amityville, New York. The house is on sale for a reason: Ronald DeFeo murdered his entire family there a year earlier. Unsurprisingly, no sooner have the Lutzes moved in than they experience unholy horrors: manifestations of flies, strange voices, ungodly cold spells, a hidden basement room, an "imaginary friend" to one child who seems very real. Most unsettling of all, George's easygoing personality transforms into a violent who seems to be channeling DeFeo, or whatever demonic presence resides in their home.
Whether or not The Amityville Horror really is based on a true story or an elaborate hoax, it's a perfectly fine hook for a horror movie. Unfortunately, Rosenberg and writer Sandor Stern present the story in strictly mechanical terms, with each scare telegraphed and every twist easily foreseen. It's not enough that the movie revisits every nightmare you'd expect from this story; the script openly cribs characters and plot points from The Exorcist, from the priest (Rod Steiger) who enters into battle with Ocean Avenue's demons to a police detective (Val Avery) who putters uselessly around the edges of the story. If Satan really was behind these disturbances, he needs some new material.
Worse, Amityville's ghost effects are so shoddy as to inspire laughter rather than terror. A subplot with a "psychic" friend (Helen Shaver) results in an absurd scene where she channels an evil spirit, Regan-style; the priest battles flies and goes blind when a statue falls on his head. George's "Jody," the daughter's imaginary friend, appears in one shot as a perfectly normal pig with its eyes painted red. The blood-dripping walls and slime-filled toilets are well-done on a technical level, but so outlandish they're impossible to take seriously. In one ostensibly terrifying scene, the children slip-slide down the blood-drenched stairs, as if having the time of their lives. Never has a demonic haunting seemed more fun!
The best that can be said about the acting is that it matches the movie perfectly. James Brolin treats George's descent into madness as an excuse to mug and scowl; we know when he starts chopping firewood that nothing good is coming. Margot Kidder, given little more to work with, at least emerges unscathed. Talented supporting actors (Murray Hamilton, Don Stroud, Helen Shaver) offer performances ranging from passable to embarrassing. But the booby prize goes to Rod Steiger, in easily the worst performance of his career. His priest swats flies, argues with his bosses, screams to the heavens and stares catatonically to convey various stages of madness, despair and an utter aversion to nuance, subtlety or recognizable human emotion.
The Amityville Horror ends with the Lutzes fleeing into a rainy night, only for George to turn back and rescue the family dog from the Hell Under the Stairs. This, at least, marks it as superior to the unwatchable 2005 remake, where George murders his poor, innocent pooch while under the house's spell. Dog lovers, at least, can take solace that there's one horror Stuart Rosenberg and Co. wouldn't perpetrate.