American filmmakers have a tendency to over-think their historical period pictures. They ply costume dramas with grandiose imagery, tediously over-written dialog and gratingly over-scored soundtracks in the hopes of overwhelming an audience with a sense of antiquity. And their actors -- especially their American actors -- often seem uncomfortable and incongruous.

Even when such films turn out well, there's always something awkward about them. Think of Francis Ford Coppola's "The Age of Innocence," Andy Tennant's "Anna and the King" or Steven Spielberg's "Amistad" -- all too conspicuously theatrical to be genuinely transporting and/or saddled with one or two actors who are amiss just enough to stand out.

But when such films turn out badly, they turn out like "The Affair of the Necklace," a discombobulated, transparently fictionalized French Revolutionary melodrama about an orphaned, impoverished aristocrat conspiring against the crown to restore her family name and property.

Hilary Swank -- turning 180 degrees from her Oscar-winning role as a delicately chiseled Nebraska transvestite in "Boys Don't Cry" -- is the movie's best asset. She plays with passion, beauty and conviction this outcast blue blood named Jeanne de la Motte-Valois, whose exploits contributed in no small part to the downfall of Louis XVI and Marie Antoinette.

When she was a child, Jeanne's anti-monarchy father was murdered and his lands were usurped by the king. Now in her 20s and in a marriage of convenience to a dubiously-titled count (Adrien Brody), she has been biding her time on the fringes of the Royal Court, plotting and trying to gain favor with anyone of influence.

But director Charles Shyer (who's previous films have all been light fare like "Baby Boom" and the "Father of the Bride" remakes) is so hung up on making Jeanne sympathetic that her ensuing deceptions have no deliciousness. Instead of embracing her machinations (a la "Dangerous Liaisons") Shyer counters every lie, every duplicity with a moment of insistent earnestness -- and the two personality traits never mesh, despite Swank's best efforts.

Aided and abetted for no discernable reason by a roguish, rather fey chevalier/gigolo (Simon Baker), Jeanne concocts a complex and risky scheme around the most ostentatious piece of jewelry in French history -- a 2,800-carat, 647-diamond necklace. Her plan is to trick a crooked cardinal (Jonathan Pryce, gnawing on scenery like he's been transplanted from the same role in a "Three Musketeers" picture) into buying the necklace, thinking he's doing so on Marie Antoinette's behalf. The power-hungry priest has been on the outs with the queen and he'll do anything to suck up to her.

But the bobble was commissioned for the mistress of the king's father -- before she was banished from court -- and therefore Antoinette (played as a spoiled woman-child by Joely Richardson) wants nothing to do with it. This is a fact that Jeanne leaves out of the equation while pretending to be the queen's messenger to the cardinal.

How any of this gets Jeanne closer to regaining her title and lands is not at all clear. Neither is what role the ensuing scandal played in the French Revolution, other than making Marie Antoinette look greedy when a twisted version of the facts comes to light after Jeanne is arrested.

As a result of trying to fill in the movie's gaping holes in your own mind, a slew of other questions arise and it's not long before you can't help but be watching for mistakes. How can the cardinal be convinced his relationship with Antoinette is on the mend when he most certainly sees her in church and get a cold reception? How do Jeanne and the gigolo (who seems quite clearly gay until, out of nowhere, the two have a torrid love scene) fake Antoinette's handwriting on letters to the Cardinal? How and where did they acquire the royal seal to stamp said letters?

A myriad of other narrative conundrums arise over the course of the picture (gauging the passage of time is a real challenge throughout the film). But where Shyer really fails the audience is in cutting down his heroine's eventual trial -- potentially a great source of drama and his last opportunity to clarify the baffling story -- to nothing but a montage sequence.

At its best "The Affair of the Necklace" might make you yearn to read a book or find a French film on the same subject to get at the intricacies of these events without the cosmetic eloquence, the questionable performances and elementary filmmaking. At its worst, Shyer's direction is so uncouth that he cuts away to flashbacks (that we've already seen) of little Jeanne watching her father killed, rather than showing the emotions of the memory play across Swank's incredibly expressive face.

A true talent, Swank emerges from the film unscathed in spite of her character's gross inconsistency. Here's hoping this doesn't send her career crashing back into the B-movie doldrums from whence she came.