We’ve all loved someone crazy, and -- go on, admit it -- we’ve all been the crazy person someone loved. Madness, even when temporary, has an allure that leaves common sense waving frantically in the rearview mirror, growing smaller by the second. There’s something almost intoxicating about mind-to-mind and body-to-body contact with someone who’s simply not inhaling the same planetary atmosphere that you are. And when said kookiness is combined with real intelligence, the combination is enough to send even the badly burned reaching straight back into the fiery ovens of amour without so much as the benefit of a padded mitt.

Dig it: while you’re quietly sorting out your taxes, your honey bun is up on the roof reconstructing a Mayan fertility rite beneath the full moon. You’re washing dirt out of the spinach five minutes before dinner, and your sugar lamb is down in the basement realigning the rudder on that damned ark. Whatever the scenario, one thing’s for sure. Crazy love promises to virtually inoculate you against a future in which you’ll spend endless tedious hours together, the silence punctuated only by a question about whether you’ve paid the car insurance yet.

Few actresses play loopy as sexy with the virtuosity that Australia’s Rachel Griffiths routinely displays in "Six Feet Under," the thinking person’s soap opera created by "American Beauty" director Alan Ball for the US cable channel HBO. For those without the questionable benefit of a cable subscription (or, for that matter, the questionable benefit of American residency), Rachel appears as Brenda Chenowith -- part-time bodyworker, full-time hedonist and most-of-the-time partner of Nate Fisher, the handsome thirty-whatever manchild around whom the series loosely revolves.

Brenda comes with a troubled present equal to her troubled past. She was child genius raised by psychiatrists, and studied by still more psychiatrists. Her experiences became the subject of a classic child psych text -- a book so well-known that it keeps Brenda’s distant past right on the heels of her adult self. She’s closest to her brother, Billy, a good photographer with the bad habit of going off the medication that controls his manic-depression. Close enough, in fact, that Brenda and Billy had the names of their fictional childhood alter egos tattooed on the small of their backs. Billy’s anesthetic-free home removal of his tattoo -- and his attempt to perform similar surgery on Sis -- is one reason why she’s reluctantly had him committed..

Out of this turmoil comes an unpredictable character at once worldly, funny, cynical, animal, potentially scary and profoundly sorrowful: woman as dry martini with a nitroglycerine chaser. She’s not one for blindly following convention. Introduced as Nate’s partner, she fires back, "I prefer the term ‘fuck puppet.’"

If consistency equals sanity, then Brenda is a few crustless cress sandwiches short of the proverbial picnic; Nate never knows which Brenda he’ll get and, fortunately, neither do we. Brought up to believe that she’s surrounded by idiots, she’s afraid to drop her guard lest someone hijack her heart. Or, as the character herself puts it with characteristic bluntness, "Every time I’ve believed in a happy ending, I’ve gotten severely fucked."

In lesser hands, Brenda would be a bug-eyed caricature, or -- worse -- a generic two-dimensional bad girl with a smart mouth. But Griffiths achieves more by emoting less, turning down the histrionics to communicate through expression, gesture and timing. A whole range of emotions can flicker across her face in seconds, from amusement and concern to a radiantly goofy innocence. During a recent "Six Feet Under" sex-fantasy sequence, the camera settled happily on the play of feeling lighting up the Griffiths visage, with results that threatened to melt the circuitry of TV sets across America.

This is the actress described by the Guardian in 1998 as "a wild card with an acute intelligence, a fierce laugh, and a slight air of sadness," who reads contemporary philosophy and psychology in her spare time. She was born in 1968, raised by a mother with an artistic streak, and launched her career after university with a stint in a Melbourne community theatre group. Griffiths went on to create and perform "Barbie Gets Hip," a 1991 Melbourne Film Festival entry.

Her "Six Feet Under" part may show us the Tart of Darkness, but Griffiths’ international breakout role in "Muriel’s Wedding" offered a more take on the theme that’s more sweet than bitter: the eponymous heroine’s party-girl pal with a flair for lip-synching Abba. The film brought Griffiths both the Australian Film critics award and the Australian Film Institute’s award for best supporting actress. It also brought her a place the thespian big time, launching her on a string of film roles which showcased her versatility. Among them: a backpacking Aussie who takes a job working on high power lines in England ("Among Giants"), a London prostitute involved with an Anglo-Pakistani taxi driver ("My Son the Fanatic"), a single woman wondering what life with marriage and children would have been like ("Me Myself I"), and the mother of an ambitious drug dealer ("Blow").

Griffiths’ performance in "Hilary and Jackie," the biopic about cellist Jacqueline du Pre, elevated her career yet again. Her restrained portrayal of du Pre’s older sister -- playing opposite Emily Watson in the title role -- led to an Academy Award nomination for Best Supporting Actress. Factor in a Golden Globe in 2002 for her work in "Six Feet Under," and Rachel Griffiths appears to have reached that international tipping-point at which "familiar face" ends and "household name" begins.

At this writing, Griffiths’ latest US cinema release is the less-than-gratefully-received "Very Annie Mary," from "Mad Cows" director Sara Sugarman. Like Sugarman’s previous project, it’s been slammed for faults including a shaky plot. Even so, the BBC found it "worth catching for Griffiths' warm and winning central performance."

Then again, you can’t strike gold every time if you work hard and take risks, and Griffiths is both a hard worker and a risk-taker. Her hefty filmography testifies to her dedication. And her willingness to flirt with chance shows up not only in her broad choice of roles, but off the screen as well. Consider her protest at the opening night of Melbourne’s big late-Nineties casino, a project the self-described architecture freak dismissed as "a big ugly conglomerate pimple." Griffiths arrived in the requisite flashy limo, only to emerge in a costume reportedly inspired by both Lady Godiva and Jesus. It may have been the biggest gamble of the evening -- no small achievement at a casino opening.

Perhaps that convention-shattering streak informs Griffiths’ performance on "Six Feet Under." The program’s other characters may ricochet between satisfying their own desires and meeting the expectations of others, but Griffiths’ Brenda Chenowith is never less than completely herself. In fact, you know what? Forget crazy. She’s actually the sanest one of all.

In art and in life, Rachel Griffiths doesn’t just walk on the wild side -- she cavorts through it with verve and wicked laughter. Now, that’s my kind of Tart icon. Film

• Muriel's Wedding (1994)
• To Have and to Hold (1996)
• Children of the Revolution (1996)
• Cosi (1996)
• Jude (1996)
• My Best Friend's Wedding (1997)
• Welcome to Woop-Woop (1997)
• Since You've Been Gone (1998)
• Amy (1998)
• Divorcing Jack (1998)

• My Son the Fanatic (1998)
• Hilary and Jackie (1998)
• Among Giants (1999)
• Me Myself I (1999)
• Very Annie Mary (2000)
• Blow Dry (2001)
• Blow (2001)
• The Rookie (2002)
• The Hard Word (2002)

• Since You’ve Been Gone (1998)
• Jimeoin (1994)
• Secrets (1993)
• The Feds (1993)
• Six Feet Under (current)