Shock aka Beyond the Door II (1977)

The last film by another great Italian horror specialist, Mario Bava, whose output has been far less consistent than Argento's.  He was capable of great style, for example in his early film "The Mask of Satan", but perhaps he worked too broadly or too quickly or in too many genres.  This dubbed idiocy which is a cross between an "Exorcist" rip-off and a gesture to "Hamlet" (why did you kill my father?) features Daria Nicolodi (also to be seen in "Inferno" below) as the troubled and threatened mother.  There are a few good scares -- see her attacked by the furniture!! -- but these are few and far between.  And if I had a creepy son like hers I might have nightmares as well.