Lady Macbeth is excited by her role in the plot to kill Duncan. She has drugged the soldiers' wine, but when she hears movement, she thinks that one of them is awake. She worries that her cowardly husband won't be able to complete the murder. But she is relieved when she sees that the noise that she heard was her husband returning with the soldiers' daggers covered in blood.
Macbeth tells his wife that after he murdered Duncan, he heard Malcolm and Donalbain wake, and one of them shouted "Murder." Macbeth then heard them pray and, for the guilt of his sin, he could not even say 'Amen' to their prayer.
Then he thought he heard a voice say that he had killed sleep and that he would sleep no more because of his crime. His imaginings reveal his fear, and he refuses to return the daggers to Duncan's body because he is afraid to look upon his crime. He's afraid that the stain of Duncan's blood will not clean off his hands. Lady Macbeth takes the daggers back to Duncan's body and smears the king's blood on the sleeping soldiers so that it incriminates them for the murder. She warns her husband that thinking about the murder will drive them insane. Suddenly there is a knock at the castle gates, so Macbeth and his wife hurry to change into their nightclothes and wash the blood from their hands.
