I really can’t remember much. I only saw it once when I was a kid. What I can remember is the guy lived in what I assume is a haunted hause. In one scene he falls through the bathroom mirror and ends up in Vietnam I think. I may not even have the details right, it might be multiple scenes mashed together.
This horror comedy was directed by Steve Miner, who also directed two of the Friday the 13th films.
A writer inherits a house from his aunt. Years earlier his son disappeared from his swimming pool. The boy was never found and the writer’s marriage fell apart. He begins to see supernatural beings in the house, including a witch who threatens the toddler son of his attractive neighbor. The main antagonist is the rotting corpse of someone from his platoon who died in Viet Nam. The guy blames the writer for his death and wants revenge. He is the one who abducted his son and holds him in another dimension. To get his child back, the writer lowers himself by rope through the bathroom mirror (a portal into another dimension). Back in the jungles of Viet Nam he has to do battle with the dead soldier to rescue his son.