“Obsession” (** out of four) was a fairly predictable Southern potboiler about a drifter (Mekhi Phifer) who is taken in by a wealthy landowner (Brad Dourif) and starts a steamy affair with his wife (Elika Portnoy) and they conspire to kill him and free her from her loveless marriage. Not all that different from “The Postman Always Rings Twice” except this one lacks atmosphere and sizzle. Good performances help keep it watchable but it never ignites like it should.