In Macbeth by William Shakespeare, Lady Macbeth is very central to the development of the plot of the story. Lady Macbeth changes from Macbeth's ambitious, power hungry wife into a contrite, guilt-ridden deranged person.
At the beginning of the story, Lady Macbeth seems like a pretty average, mentally stable wife of a noble. However, it is important to remember that looks can be deceiving. When Macbeth returns from speaking with the three witches and tells Lady Macbeth about their prophecy that he will be Thane of Cawdor, Thane of Glamis and King of Scotland, Lady Macbeth is elated. She immediately starts imagining her life as Queen of Scotland and starts plotting to kill anyone who gets in her husband's way.
As the story goes on, Macbeth and Lady Macbeth act out Lady Macbeth's plan to kill Duncan and seize his throne. They kill Malcolm and Macduff in order to bring Macbeth closer to kingship, but Lady Macbeth still shows no remorse for her horrible doings. They then kill Duncan and become king and queen of Scotland. It seems as though the witches' prophecies have been fulfilled. Lady Macbeth now has the royalty that she has always wanted. However, people are seldom happy with what they wish for.
Ultimately, Lady Macbeth's attitude towards her actions changes. She becomes so guilt ridden and contrite that she begins to hallucinate and slowly goes insane. In Act 5, Scene 1, she retells the story of Duncan's murder. She says, " 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?-Yet who would have thought the old man to have had so much blood in him" (5.1.25-29). When she says "damned spot", she is not just talking about the imaginary bloodstain on her hand; she is also using it as a metaphor for the fact that she has guilt in her heart that will not go away.
In conclusion, Lady Macbeth's personality and ambitions change throughout Macbeth. This is because she acts on instincts rather than logically thinking through possible choices when she decides to kill a handful of other characters in order to become queen. She takes advice from the witches, who may not even have been telling the truth. The fact that Macbeth is a tragedy may be largely attributed to her actions, her schemes, and that she succumbed to these very actions and schemes.