It opens with two nervous people living in a cold, threatening house. They hate or fear each other, we sense. She wants to stay home and read. Cut back home. An envelope is found on their steps.
More tapes arrive, including one showing the wife's murdered body in bed.
As a matter of fact, I'm there right now. He does seem to be at both ends of the line. That mirrors another nice touch in the film, which is that Pullman seems able to talk to himself over a doorbell speaker phone. Halfway through the film, Pullman is arrested for the murder of his wife and locked in solitary confinement. The prison officials can't explain how bodies could be switched in a locked cell, but have no reason to hold the kid.