The gnarled Australian import Lantana takes its name from a native bush that snares the unwary. This parched but intense film, directed by Ray Lawrence (''Bliss'') from an adaptation of an even more gnarled play by Andrew Bovell, is one of those choking dissections of carelessly untended adult relationships in which every married anybody stumbles and trips while deceiving their somebody.
Sometimes the sin is one of commission, as in the ambivalent, casual sex between Leon (Anthony LaPaglia), a grim, tired police detective, and Jane (Rachael Blake), a hungry, destructive woman with whom Leon and his suspicious wife Sonja (Kerry Armstrong) share salsa dance lessons. Sometimes it's one of omission, as in the neurotic paranoia with which Valerie (Barbara Hershey), a psychotherapist, comes to believe that her husband (Geoffrey Rush) is having a homosexual affair with one of her patients. It's one of those remarkable theatrical coincidences that Sonja happens to be Valerie's patient. And that when Valerie disappears one night, Leon is called upon to investigate.
Neither writer nor director supply good reasons why these miserable moderns do what they do. But this leaves the actors to do what they like. And in this, ''Lantana'' blooms with talent, particularly in LaPaglia's lived-in performance as a man lost in a thicket of middle age.