VIDEO: Michelle Williams on 'Nightline:' Heath Ledger, 'Blue Valentine'

In an emotional interview, she breaks her silence on her ex's death.

In an emotional interview with Nightline, Michelle Williams opens up for the first time about her ex Heath Ledger's death of an accidental drug overdose.

Williams, who has a daughter, Matilda, 5, with Ledger, also discusses what it was like to work with Ledger on Brokeback Mountain.

Ryan Gosling also briefly appears, and the two talk about filming Blue Valentine, and playing an on-screen couple.