In the final major piece of casting in “The Da Vinci Code,” Paul Bettany will play the albino fanatic, Silas. Ron Howard is directing the Akiva Goldsman-scripted adaptation of the Dan Brown novel, with Tom Hanks and Audrey Tautou playing the lead roles. Ian McKellen, Alfred Molina and Jean Reno recently joined the cast. McKellen plays Sir Teabing; Molina is set as Bishop Aringarosa, the head of Opus Dei. Reno plays the gruff detective who suspects Langdon of murder.