MACDUFF: Our royal master ‘s murder’d!
LADY MACBETH: Woe, alas!
What, in our house?

– William Shakespeare

Macbeth, Act 2, Scene 3. When Macduff announces the murder of King Duncan, Lady Macbeth plays the part of the innocent, when in reality she plotted the King’s murder. She acts shocked and sad, when in fact she already knew Duncan had been killed by her husband at her instigation.