Delving into the horrific history of the infamous Long Island haunted house, this prequel to 1979's popular chiller The Amityville Horror is loosely based on the DeFeo murders but is at heart a straightforward horror-exploitation film with an Exorcist twist. When the violently dysfunctional Montelli family moves into the rustic abode (claimed to have been built on an Indian burial ground), the standard haunted-house clichés (bleeding walls, swarms of flies, bubbling black goop) give way to a more direct demonic attack on the eldest son -- who develops an unhealthy interest in his nubile younger sister, followed by a much more lethal attraction to dad's shotgun. In a desperate attempt to purge the evil, the local priest tries to perform an exorcism...with unexpected results.