A haunted house epic with a perverse domestic twist or two, Shock is perhaps middling Mario Bava, but it has some memorable images and maybe even a shock or two.
A couple and their son moves into a house that they probably should have avoided altogether. The wife Dora, played by Argento regular Daria Nicolodi, is understandably uneasy about moving back into the house, where her first husband, a junkie, killed himself, but her new husband Bruno, played by John Steiner also from all sorts of Italian flicks, insists on it- quite the sensitive husband there. (To round out the feeling that we're with the Italian exploitation repertory company, Ivan Rassimov shows up as a doctor.) Making matters worse for Dora, their son Marco is one of those little kids in movies who are easily amused by paranormal happenings in old houses, and he's at that difficult age where they're so susceptible to being possessed by their dead fathers.
What's fairly effective about the movie is that Bava keeps it unclear whether the kid is possessed, the father's ghost is haunting the joint, or they've just got a brat for a son. Marco resents his mother's relationship with Bruno and makes all sorts of difficulty, at one point telling his mother that he has to kill her. He may or may not have sent her flowers, allegedly from her dead husband. At one point, Marco pretends to hump her. Before long, things start moving around the house on their own and Dora is hallucinating rotting hands grabbing her. She starts slipping in her domestic duties, leading Bruno to remind her, "There's nothing worse for a marriage than sending a husband off without his coffee". Nothing? One would think being haunted by a vengeful junkie ghost would cause more problems.
The strength of these haunted house films is their atmosphere. Bava does a good job here with the sound design and striking visuals, such as a scene in which Nicolodi's hair goes every which way as she lies in bed and another in which Marco suddenly becomes the dead husband. Admittedly, as with most of these movies, there's only so many scenes you can take of people wandering around hallways and basements alone. Also, even after the plot reveals its dark secrets and explains why Bruno and Dora moved back into the house it doesn't really make sense. But, there are some good moments of fear and Bava and Nicolodi knew what they were doing by this point, so it all works out.