The actress Charlize Theron has been used by Hollywood mostly as a small, decorative bangle on the arm of thrillers like "The Italian Job" and "15 Minutes." Her appearance in "Monster," then, comes as a discombobulating shock. She's huge. She's been given the sort of physical makeover that begs for Oscar nominations -- dowdy hair, false teeth, mottled skin -- but it's the size of the performance that's transformative. Wide-shouldered and thick-waisted, Theron bullies her way through the film as if she wanted to pick a fight with the cast and the audience: she's a Frankenstein monster fueled by extra jolts of aggrieved, class-conscious rage. That Theron is playing Aileen Wuornos, the self-confessed murderer of seven men who was put to death by the state of Florida in October 2002, may cause problems for some. This sort of project -- in which a beautiful starlet de-glams for a tour of the lower depths -- is easy to mock, and many will feel Wuornos doesn't deserve the attention, let alone the sympathy. Writer-director Patty Jenkins hasn't made her case any easier by telling this story with a minimum of frills. "Monster" doesn't forgive its subject for her sins but it doesn't give you much reason to care, either. It's stranded between the tabloid tragedy of 1986's "Henry: Portrait of a Serial Killer" and the inspired melodramatics of the more recent "Boys Don't Cry."
What it has going for it is Theron's pitiless, intensely felt performance as a woman so inured to the dregs that she explodes with hope and psychosis when she gets a glimpse of something better. Aileen is a truck-stop prostitute with a battered past -- the movie leaves out the real Wuornos's even more horrific childhood -- who has been surviving on the brief attentions of men until the night she wanders into a Daytona gay bar and meets Selby Wall (Christina Ricci). A stand-in for Wuornos's real lover, Tyria Moore, Selby is a shy little thing who lives with her holy-roller aunt and uncle; she feeds off Aileen's aggressive attitude even as Aileen finds in Selby the first real love she has known.
Aileen towers over Selby like a beefy, obstreperous Mutt to her Jeff. The two move in together, and Aileen has fantasies of living legal that are dashed by her unsuitability for any sort of job. She falls back on tricking, and when one of her pickups gets sadistic on her, she kills him in self-defense and buries his remains in a swamp. The next six are easier, even as the men beg for their lives.
"Monster" presents those killings with sad bluntness, as Aileen tries to stop her ears to her victims' pleas and maintain her vengeful fugue state. The movie doesn't make her out to be insane -- her cup of anger has simply, disastrously runneth over -- but it does ask us to feel for Aileen as she scrabbles desperately after a "normal" life with Selby. That stupid dream recedes the more the two run from motel to motel, toward the reckoning that every one except the murderess knows is coming.
The audience might even believe in that dream if Ricci held up her end of the bargain. Initially charming in a bruised wallflower way, Selby has become a tiresome whiner by the end of "Monster," and I don't think that was supposed to be the point. The filmmaker also omits any mention of Arlene Pralle, the born-again Christian who befriended Wuornos after her 1991 arrest, defended her in the pages of Vanity Fair, and legally adopted her because "God told her to." That sounds like an interesting movie, if a different one.
Instead, "Monster" is a gruesome, helpless spiral barely saved by an actress locating humanity where few would have cared to bother. Theron's Wuornos is the flip side of our obsession with female beauty and propriety -- she stalks the Florida highways like one of R. Crumb's demon-women unleashed. It's the kind of performance that seems calculated to attract the Academy's attention, except for one thing: I forgot all about Oscar, and Theron, as I was watching it.
Ty Burr can be reached at email@example.com.