There are taut, gripping noirs and then there are convoluted messes. There are unpredictable plot twists and then there are randomly chaotic events. There are relatable factors that drive a character's behavior and then there are the inexplicable wild mood swings between severe emotional distress and uncontrollable horniness that seize the characters in "The Black Dahlia."

The pedigree of this film is impeccable. Brian De Palma, director of such solid crime dramas as "The Untouchables" and "Scarface," is at the helm. The result, though, is a bewildering, disengaging take on one of the most sensational murder mysteries in Los Angeles history.

The Black Dahlia was a 22-year-old wannabe actress named Elizabeth "Betty" Short who was found slain in a vacant lot near Leimert Park in 1947.

She was naked, splayed, cut in half at the waist and disemboweled. The killer had bludgeoned her, sodomized her, removed her reproductive organs and slit her mouth from ear to ear in a sickening grin.

The crime remains unsolved today and one would think a film about the ensuing investigation would be filled with intrigue and drama.

Instead, the narrative is unfocused to the extent that the Dahlia becomes only incidental to the plot. We follow more closely the exploits of Dwight "Bucky" Bleichert (Josh Hartnett), an investigator on the case.

This, in itself, would have been acceptable if he, or any of the other characters he encounters, were given just a smidge of psychological depth and motivation for their actions.

Don't blame the actors. Though Hartnett's mumbling voice-over is frustratingly unintelligible, he miraculously manages to engage the viewer throughout this head-scratcher of a film.

Aaron Eckhart, who plays Bleichert's partner Lee Blanchard, Scarlett Johansson (Blanchard's girlfriend Kay Lake) and Mia Kirshner (the Dahlia herself) all do decent jobs fleshing out their two-dimensional cardboard characters.

Hilary Swank (construction heir Madeleine Linscott) deserves a special mention for taking this acting gig seriously even though she is forced to wear what appears to be a frizzy shrub atop her head for most of the film. Her perm is so hideous that whenever her character puts on a hat, this reviewer heaved a sigh of relief.

The sprawling and talented cast is sadly underused. Most of the actors are either given too little to do or are obliged to become unintentionally laughable as they play out the movie's ludicrous scenes.

Poor writing explains away their innermost demons with throwaway expository lines without ever showing us who these people are or what they really want. This makes it impossible for the audience to sympathize with their moments of anguish.

One cannot help but snicker when the characters leap into bed with each other without the slightest provocation.

"The Black Dahlia" is not completely devoid of pleasure. The trademark De Palma set pieces of violence and gore are top notch, and the 1940s atmosphere has been recreated meticulously in the cinematography, sets, costumes and makeup. K.D. Lang makes a cameo as a singer in a lesbian club -- and there are funny moments that were intended.

The camerawork is often stunning, with long, elaborately designed shots that elegantly cover the geography of the characters and propel the story forward. This occasionally backfires when the camerawork calls attention to itself or when the characters come distractingly in and out of focus, thereby breaking the film's already flimsy illusion.

"The Black Dahlia" fails to spin an interesting or meaningful yarn. Unless you worship Brian De Palma or are a rabid Hartnett/Johansson fan capable of switching off your brain and just watching the pretty pictures, please steer clear.