Why was Heath Ledger so ambivalent about his own stardom, and what happened at the end of his life? Vanity Fair contributing editor Peter Biskind sheds new light on these difficult-to-answer questions as he writes about the actor's remarkable talent and untimely death in the August cover story, "The Last of Heath."

In his article, Biskind explores Ledger's final movie role, his uncertainty about Hollywood, his devotion to his young daughter, and what happened in the days and weeks leading up to his death as he battled chronic insomnia, pneumonia, and exhaustion. Here are some of the revelations contained in Biskind's story.

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How he cleaned up his act

Cinematographer Nicola Pecorini, who worked with Ledger on his last film, The Imaginarium of Doctor Parnassus, says Ledger "used to smoke marijuana on a regular basis, like probably 50 percent of Americans." But after it became an issue, Ledger "went clean as a whistle." And vocal coach Gerry Grennell, who worked and lived with the actor during the filming of The Dark Knight, says Ledger even stopped drinking: "Heath would happily go to the bar, buy a round of drinks for friends, and come back and have a soda or juice, never once drinking alcohol."How chronic insomnia may have led to his death

Ledger's use of sleeping medication to combat chronic insomnia at the end of his life was of more concern to Grennell. "I'd say, If you can possibly bear it to stop taking the medications, do, because they don't seem to be doing you any good.' He agreed. It is very difficult for me to imagine how close he came to not taking them."

Ledger would typically spend night after night awake, diverting himself with time killers, Biskind reports, such as re-arranging the furniture in whatever space he happened to be living in at the moment. Grennell coached him in the Alexander Technique, which helped him to sleep for a few hours at a time, but he still struggled.

"Everyone has a different view of how he passed away," Grennell tells Biskind. "From my perspective, and knowing him as well as I did, and being around him as much as I was, it was a combination of exhaustion, sleeping medication … and perhaps the aftereffects of the flu. I guess his body just stopped breathing."

How his relationship failed

Terry Gilliam—Ledger's friend and mentor, and the director of Doctor Parnassus—agrees with Pecorini that the romance between Ledger and Williams began to unravel during the Oscar campaign for Brokeback Mountain. "The whole machinery started growing up around them," Gilliam says. "That was the moment when it changed, when he realized, Uh-oh. We perceive the world differently. He didn't care about things like those awards."

According to Pecorini, "Heath was always blaming himself [about the relationship], asking, What did I do wrong?" Adds Gilliam, "Because he's a much nicer person than I am, he really thought he could do the right thing. He was trying to be decent and graceful, give her whatever she wanted—the house, every fucking thing. But once it started going south, it went very quickly. He was overwhelmed by lawyers, and there were more and more of them, as if they were breeding. I said, This is bullshit. Heath, just end it. Get out—it's bad. You've got to just walk away from it.' The stakes kept going up. He wouldn't listen to any of us."

As Ledger's relationship with Williams unraveled, and the pair started dealing with lawyers and custody issues, according to Gilliam, Ledger fell apart. "The thing that really made Heath snap" was legal wrangling over his daughter, Matilda, Gilliam says. "He said, Just fuck all of you! I'm not giving Michelle anything.'???" Recalls another source, when it came to Matilda's care, "there were definitely heated conversations, and emotions were high." (Ledger's lawyer declined to comment on any aspect of the separation or custody dispute.)