 Lady Macbeth is a powerful presence in the play , most notably in the first two acts . Following the murder of King Duncan , however , her role in the plot diminishes . She becomes an uninvolved spectator to Macbeth 's plotting , and a nervous hostess at a banquet dominated by her husband 's hallucinations . Her fifth act sleepwalking scene is a turning point in the play , and her line , " Out , damned spot ! , " has become a phrase familiar to many speakers of the English language . The report of her death late in the fifth act provides the inspiration for Macbeth 's " Tomorrow and tomorrow and tomorrow " speech . 
