Macbeth (opera)
Lady Macbeth reads a letter from her husband in which he tells her about the prophecy the witches had made.  She decides to make sure that Macbeth really does become king.  She decides that she must persuade her husband to murder Duncano (Duncan, King of Scotland).  Macbeth sees a dagger in front of him.  He takes it and murders Duncano (who never sings in the opera).  Then he is horrified at what he has done.  His wife is disgusted that her husband feels terrible about the murder.  She takes the dagger and completes the crime, then smears Duncano’s blood on the guards who are asleep.  Banquo and Macduff, a Scottish nobleman, arrive, Macduff discovers the crime, and all the characters sing a chorus asking God to punish the murderer(s).