He was always disappearing, into a role, out of the starlight. A heartthrob at 20 as Mel Gibson's son in The Patriot, this Australian émigré eluded fans by being nearly unrecognizable from film to film. He took small, gnomish parts (in Monster's Ball and The Lords of Dogtown), then exploded back into celebrity with his role as the bisexual cowboy a rich portrait of emotional incoherence in Brokeback Mountain. A star again, he vacated movies for a year to help raise his daughter Matilda, by Michelle Williams, who played his wife in Brokeback. Ledger completed his most dynamic role, as the sauntering psycho Joker in The Dark Knight, just before dying at 28 of an accidental overdose of prescription drugs. The movies' most audacious, least knowable young actor had disappeared for good.