This time out, there's no vat of chemicals to explain how Batman's greatest enemy came to be the twisted sociopath known as the Joker.

Heath Ledger's Joker springs full-blown in this summer's "The Dark Knight," the sequel to 2005's "Batman Begins" that was previewed for theater owners Thursday with a clip showing the new movie's opening sequence.

Unlike 1989's "Batman," in which the deranged, disfigured clown appearance of Jack Nicholson's Joker resulted from a dip in chemical goo, "The Dark Knight" starts right in with the bad guy in all his psychopathic glory.