A ferocious tour de force

When Charlize Theron won the Best Actress Oscar for Monster last month, there was much knee-jerk critical sniping. Although the film hadn't even been released in the UK yet, many commentators were quick to write off her victory as Hollywood rewarding yet another beautiful women for making herself ugly - see Nicole Kidman, Renee Zellweger et al.

But there is so much more to Theron's performance than just her - albeit convincing - appearance. It's a depiction that lingers with you, wondrously and tortuously.

The story of Aileen Wuornos, who was executed in 2002, is infamous. A drifter prostitute in Florida, she killed seven 'johns' before being caught, villified as America's first female serial killer.

When we first see Aileen, she is sitting bedraggled underneath a motorway bypass, contemplating suicide. The product of a sexually abusive and violent childhood and 'hooking' since she was 13, her appalling life is graphically realised in Theron's characterisation.

As Aileen, Charlize swaggers around, a feisty, jittery figure, her arms flailing, her mouth permanently jutting and turned down on her sunburnt, shiny face. The picture quality is dirty and scrubby, a filmy mirror holding up the grubby reflection of her life.

Aileen meets the cherubic-looking Selby (a strangely unconvincing turn from Christina Ricci), a young lesbian who naively seduces her. Initially resisting her approaches ("I ain't no f***ing dyke"), Aileen begins to fall for this romantic figure, so small that even cigarettes look big in her mouth. She offers her the first love in her desperate life, and so they begin a sweet courtship, full of fantastical futures and a driving desire to escape.

Then the tone of the film takes a horrifically darker turn. A john turns violent on Aileen, smashing her head, tying her up, raping her. To escape death, she grabs the man's gun and shoots him dead. Taking Selby with her, the two go on the run in his car, and Aileen decides to quit the street and begin a new life.

We know in our hearts this won't work and of course, it doesn't - the uneducated Aileen has no ability to function in the world of offices and bureaucracy, and her hopeless, heartbreaking attempts to find a job ("I might be a vetinarian. Or a businessman," she speculates) inevitably result in failure.

"I'm starving," says Selby - who is selfish, and whiny. Neither of this artless pair consider that she might work, so it's down to Aileen, and she gets money in the only way she knows how. But this time, she knows there's a better way - no sex, only murder. Thus begins her terrible descent into maniacal acts of homicide. As she commits more and more crime, Aileen begins to take on a crazed glaze of confidence. You see it immediately: she believes this is the way to control her life and be happy. Kill the men, steal their money, give it to Selby and she'll carry on loving her.

Trickling through our consciousness throughout the course of this film is the end we know is coming. And it does. But the way in which we get there is the rewarding element and the pivotal to it is the central, paradoxical figure of Aileen. Neither martyred nor villified, it is one of the most excrutiatingly honest portrayals of an anti-hero seen on screen. She frustrates us, angers us, infuriates us, sickens us. Yet it's impossible to dismiss her, and possible, even to like her.