The star of Brokeback Mountain, Ledger is slung back in his seat, his long legs stretched out in ratty jeans, a hood pulled over his dusty brown hair. In movies, the high cheekbones slash across the screen. In person, he merely looks indistinct, curiously unassuming.

"This is my life when I'm in New York. I drive Michelle everywhere," he says, referring to his partner and Brokeback Mountain co-star Michelle Williams.

As he cruises up the West Side Highway, the Australian chats about the rapid life changes of the last couple of months, when he sold his bachelor pad in LA and moved east.

In a way, Ledger is shy about his public transformation. This fall shows him in a pair of contrasting roles. Casanova, in which he plays the raffish title character, showcases his able comedic chops. Ledger's other film, Brokeback Mountain, is the one that represents his evolution from dude to one of the most wrenching and poignant actors of his generation.

Save for several potent minutes in the indie Monster's Ball, there's little in his resume - from his American debut in 10 Things I Hate About You to the Arthurian romp A Knight's Tale and the action-adventure The Patriot - that prepares the audience for the depth of Ledger's Ennis Del Mar, the cowboy at the center of Brokeback Mountain.

Based on an E Annie Proulx short story, the US$13 million (HK$101.4 million) film, directed by Ang Lee and shot in Calgary, Canada, is the tale of two dirt-poor cowboys (Ledger and Jake Gyllenhaal) and their love for each other, carefully suppressed and hidden from the world around them.

Ever since it won the top prize at the Venice Film Festival in 2005, the film has been known in Hollywood as "the gay cowboy movie."

As Ennis Del Mar, Ledger emits the kind of loneliness that seeps into your bones like the dampness of a bad winter cold.

He's unvarnished, understated and stoic, fiercely determined to keep his longing, fury and grief pent up for the rest of his life.

Catharsis isn't permitted in his unforgiving cowboy world.

"When I met him, the moment I saw him, that was it. He nailed it," Lee says.

"He's the person that's the best to carry that western brooding mood - elegiac and fearful and violent, all the complexities, all the poetic qualities."

Ledger's ease on horseback - and directors' penchant for casting him as someone who rides - might owe something to the fact that his stepfather owned a farm.

"I used to chop wood. That was my chore. I grew up around horses. Funny enough, I didn't start to ride horses until I had to. Then I couldn't get off horseback."

He says he essentially fell into acting at the instigation of his sister's agent, who got him cast in an Australian TV show.

"I've known Heath for a long time," says James Schamus, Lee's producing partner. "I always thought he was underserved in a lot of the roles he did."

Ledger knew from the moment the Larry McMurtry-Diana Ossana script for Brokeback Mountain dropped into his lap that he wanted to play Ennis. He even told the filmmakers he'd fly to China just to meet Lee.

"I enjoyed the stillness, and I enjoyed the lack of words on the page. There was so much information about him in the short story, I knew how to play those silent moments," he says.

"Whether or not Ang created that environment for me to work and live in, or I created it for myself - it's a lonely story, so it's hard not to take it home with you and feel lonely."

He admits that both he and Gyllenhaal were "very, very nervous" about the gay love scenes - which are straightforward and unusually frank.

"It's easy to say it was difficult and hard, but it's really awkward having to do a love scene with anyone - whether it's a guy or a girl. There's a guy with the boom standing over you. It's always awkward."

Ledger recovered by flying to Venice for six months to play the title role in Casanova - as breezy and romantic as Brokeback is meticulous and spare.

"I don't really like to do the same thing twice," he admits.

"When I get cast in something, I always believe I shouldn't have been cast. There's a huge amount of anxiety that drowns out any excitement I have toward the project. Pretty much any time I've signed on to a movie, I've tried to get out of it."

LOS ANGELES TIMES