Idris Elba plays Derek Charles, a very successful asset manager for a financial firm. He has just purchased a large home which he plans to share with beautiful wife Sharon (Beyonce Knowles) and their infant son. One morning, Derek arrives at his office to find a gorgeous blonde temp secretary named Lisa (Ali Larter). He shows her some basic kindness; she responds by flirting outrageously. When Sharon gets word of the comely new employee, she's none to happy, for obvious reasons: she was Derek's secretary when they fell in love.

Derek insists that he is not attracted to Lisa, but the young woman comes on strong. She hits on him at the office Christmas party, flashes her underwear to him in the parking garage, and shows up unexpectedly at a company retreat. Each time, she insists that they are a couple and that Derek is madly in love with her. Eventually things get heated enough that Sharon finds out her husband is being stalked. A police detective (Christine Lahti) is brought in to help. If you've ever seen a psycho movie, you doubtlessly know that a police detective is the single least helpful thing in the world. It takes a pissed-off wife to finally bring an end to the madness.

I thought Obsessed was terrible, but I'm going to take a minute to acknowledge that there may be an audience for it, which I am not in. Everything that happens on the surface is lame and predictable, yet the hidden subtext may strike a chord with some viewers. Here's what I mean: The threat Lisa presents is more than just one of Derek's fidelity. While Obsessed never explicitly mentions race, the racial threat to the couple is made evident and is indicated to be far more serious. Derek Charles is a very successful black man, married to a beautiful black woman. Lisa, meanwhile, is a white woman who wants to steal him away. Over the years, there have been a number of movies - most notably Spike Lee's Jungle Fever - that have dealt with or addressed the idea of white women trying to steal away a "good" black man. The implications of such an idea are too complicated to go into here, but they are nevertheless what this film is about. I suspect some audience members - for whom that is a concern - might take a shine to the story.

For the rest of us, the picture is nothing more than a cheap, trashy thriller that adds nothing new to a decades-old formula. What's really disheartening is how manipulative the plot is. Nothing here happens organically; everything is dictated by a need to force "thrills" into the story. For example, at the exact moment that Lisa arrives to break into the Charles' home, Sharon conveniently leaves and forgets to turn on the burglar alarm. There's another moment where Lisa needs a somewhat obscure piece of information, which another character gives her, as if this person psychically knew she needed it. Because everything is so rote and so moronic, there's absolutely no genuine suspense created. Even when Lisa does something truly horrifying, it fails to register. Maybe the familiarity of the proceedings would have been less grating if the story ever even remotely bothered to define Lisa's behavior. It doesn't; she's crazy because, well, the plot needs her to be.

And really - the whole bit where a furious Sharon belatedly finds out about Lisa's interest in her husband? Things would have been a lot smoother had Derek told her about it from the start. But, of course, he didn't, because then the film would actually make sense. The late Gene Siskel used to talk about the Idiot Plot - a plot that could be resolved in five minutes, were all the characters not complete idiots. Obsessed represents the dictionary definition of the Idiot Plot.

Here's one final gripe: As much as I love James Cameron's Aliens, it set a precedent that has never gone away. In the climactic battle between Sigourney Weaver and the mama alien, Weaver - who is protecting little Newt - utters the line, "Get away from her, you bitch!" The dialogue was a rousing event at the time, but now whenever two women fight in a movie, the good one always calls the bad one a bitch before delivering the death blow. Obsessed takes this idea to the extreme, with Sharon giving four different variations on the bitch line. How many times do the filmmakers think the audience is going to cheer that?

I don't fault the actors for the movie's failure. They are all pretty good, especially Idris Elba. You can see them fighting valiantly to elevate the material. No, the fault lies with screenwriter David Loughery (who seemingly banged out this screenplay in his sleep, or had a million monkeys on a million typewriters doing it for him) and first-time director Steve Shill, who has an annoying tendency to film everything in tension-defusing close-up. I have a policy of giving every movie a fair shake once I'm in my theater seat, no matter how bad I think it looks beforehand. With Obsessed, my advance concern was that it would follow the psycho movie template closely, with no fresh angles. That concern was bourn out. Before seeing a single frame, I could have told you everything that was going to happen in it, and I'd have been right.

( 1/2 out of four)

Obsessed is rated PG-13 for sexual material including some suggestive dialogue, some violence and thematic content. The running time is 1 hour and 51 minutes.