Possible Clues:

• When the witches in 'Macbeth' say 'Double, double toil and trouble'
• When Ophelia drowns, in "Hamlet"
• Penultimate part of ''Hamlet''
• Juliet drinks the poison in it
• Chekhov play ending, often
• When Otello dies
• When Brutus sees Caesar's ghost
• When Antony says 'I am dying, Egypt, dying'
• When Carmen dies
• Last part of some plays