The level of coincidence is sometimes very hard to swallow in the Australian import “Lantana,” director Ray Lawrence’s complicated mixture of domestic drama and murder mystery. In one scene we find Pete (Glenn Robbins) walking along a Sydney street, where he’s loudly–and erroneously–accused by distraught psychiatrist Valerie Sommers (Barbara Hershey), a stranger who happens to be passing by, of harassing her; Pete retreats into a bar, where he encounters Leon Zat (Anthony LaPaglia), a cop who–unbeknownst to Pete–just happens to be having an affair with his estranged wife Jane (Rachael Blake). And that’s not all: Leon will shortly be investigating the disappearance of Valerie, and Jane will report her next-door neighbor Nik (Vince Colosimo) as a suspect in the assumed crime. One really must observe that in a city of some four million people, such a linkage among so few characters seems awfully implausible. It doesn’t really help that the other major characters–Leon’s too-trusting wife Sonja (Kerry Armstrong), Valerie’s distant husband John (Geoffrey Rush), and Nik’s spouse Paula (Daniela Farinacci)–aren’t in the loop of that sequence: they’re all closely connected to all the people who are, and so are part of the dance (a metaphor used throughout the picture) of love, betrayal, pain and forgiveness being carefully fashioned by author Andrew Bovell.

It should be fairly obvious from this that “Lantana” began life as a play: on the boards the complicated interrelationships would undoubtedly be less jarring–the conventions of the stage, after all, are rather different from those of film. Still, while the contrivances tend to pile up rather uncomfortably and some viewers will probably find the resolution of the central mystery disappointing (it’s obviously intended to point up the normalcy of the unhappiness we’re observing rather than serve as a traditional “thriller” denouement), the picture is saved (though barely) by its remarkable leads. LaPaglia, who’s sometimes been treated as a leading-man type, here flexes his thespian muscle in a character role; he uses his beefy, rather flabby body as expertly as he did as Rosedale in Terence Davies’ 2000 film of Edith Wharton’s “The House of Mirth,” painting a convincing portrait of middle-age angst. The underrated Hershey and a restrained Rush give exquisitely shaded performances as a couple trying desperately to keep up appearances in the face of marital tragedy. And while none of the other members of the cast–Armstrong, Blake, Coloimo, Farinacci or Robbins–quite matches these three, they’re all solid if unspectacular. Lawrence’s direction isn’t particularly vivid, but it does give the actors room to breathe, and the characters emerge more fully rounded than they otherwise might.

The title, of course, refers to a plant with bright blossoms but a dark, prickly undergrowth. That’s a metaphor for the story, too–and for the intertwined relationships it describes–but it must be said that in this case, the thick shrubbery easily overwhelms the pretty flowers: despite a few glimmers of hope, “Lantana” ends up as a pretty gloomy portrait of humanity. The superb ensemble, however, just makes it worth checking out.