(FROM PEOPLE) – The upcoming Batman movie, The Dark Knight, includes a posthumous tribute to star Heath Ledger, who died of an accidental drug overdose in January. The movie's closing credits will include a line that reads, ''In memory of our friends Heath Ledger & Conway Wickliffe.'' Wickliffe was a special-effects technician who was killed last September in a stunt-car accident. Ledger plays the Joker in the Christopher Nolan-directed Knight, which opens July 18. Christian Bale stars as the caped crusader, and Michael Caine, Morgan Freeman, Gary Oldman, and Maggie Gyllenhaal also have roles. (People.com)