ET's Kevin Frazier sits down with Christian Bale, Maggie Gyllenhaal, Aaron Eckhart and Gary Oldman as they remember their late co-star, Heath Ledger, and prepare for the opening of the 'Batman Begins' sequel, 'The Dark Knight.'

The cast and crew were understandably devastated when Heath, who plays the new Joker, passed away in January of an accidental overdose of prescription medication. The movie, which opens July 18, has been dedicated to the late actor and father.