In the last act, Lady Macbeth is wracked by guilt. She is so overcome with her role in the murder of King Duncan that she cannot rest. She sleepwalks, writes, and tries over and over again to wash her hands, but she cannot get the blood out because it is no longer there—it is in her mind.
The gentlewoman describes Lady Macbeth’s disturbing actions.
…I have seen her rise from her bed, throw her nightgown upon her,
unlock her closet, take forth paper, fold it, write upon't, read(5)
it, afterwards seal it, and again return to bed; yet all this
while in a most fast sleep. (5:1)
The fact that Lady Macbeth has a letter in this act parallels her first scene in the play, when she also had a letter from Macbeth. She has come full circle. At the time, she was full of ambition and did not care about the consequences of her actions. She now is wracked with guilt.
In addition to trying to write, Lady Macbeth also tries to wash her hands while sleepwalking. She cannot seem to get the “spot” of blood off of them.
Out, damned spot! Out, I say! One–two—
why then ’tis time to do't. Hell is murky. Fie, my lord, fie!
A soldier, and afeard? What need we fear who knows it,
when none can call our power to account? (5:1)
In the end, this is too much for Lady Macbeth. Shortly after this sleepwalking scene, she screams and dies. We find out later that she took her own death. First she lost her mind, then she killed herself.
This is one of the most interesting parts of the play, because in the first act neither Macbeth seemed particularly virtuous. They were willing to kill, and only for their own personal gain. There seemed to be only minor wisps of guilt. In Lady Macbeth’s case, she was shocked to see the blood on her hands after taking the knives from Macbeth and putting them back.
My hands are of your color, but I shame(80)
To wear a heart so white. (2:3)
Yet after this, both of them seem perfectly content with their roles in the murder—until Macbeth sees Banquo’s ghost. His mental instability might have also bothered Lady Macbeth, and led to her downfall. We do not know. We do know that she took a deep dive into insanity.