Possible Clues:

• Film's start
• Dramatic opening
• Curtain raiser?
• Shakespearean opener
• When, in Act III, Mercutio says "A plague o' both your houses!"
• It takes place on board a ship at sea in 'The Tempest'
• When, in Act III, Romeo cries, "O, I am fortune's fool!"
• When, in Act II, Macbeth soliloquizes, "Is this a dagger ..."
• It follows a curtain opening
• Curtain-raising time