Lady Macbeth is planning to kill King Duncan once she learns of the prophecy of Macbeth becoming king of Scotland. She essentially plays on her husband's weaknesses, calling him unmanly and weak if he will not go through with killing the king. She tells Macbeth that he needs to act innocent, welcoming, and considerate to the king but in reality, to be plotting his demise. ("Act like an innocent flower but be the serpent beneath"). She states that it will be the last time King Duncan sees the sunrise, for he will die that night by their hand. Her elaborate plan is to put drugs in the wine of the guards who stand watch by the king's bedroom, killing them so that they cannot tell what they saw, and then stabbing the king with the guard's dagger. In essence, it will appear that the guards have killed the king.
However, King Duncan reminds her too much of her father when he is asleep and so Macbeth must do the actual deed. n the morning, when the body is discovered, Macbeth lies and says he killed them out of a fit of rage for what they had done to the king; however, we know that he really killed them in order to prevent witnesses. Also, Lady Macbeth says that both she and her husband should be the most upset about King Duncan's death in order to stop suspicion from arising about them. Therefore, she pretends to be so upset that she faints when she hears the news of his demise.
In Macbeth, Macbeth is a valiant soldier, successful in battle and rewarded for his efforts. However, before he is given the title of Thane of Cawdor, he and Banquo come across the witches who foretell, "That shalt be king hereafter." (I.iii.50). This excites Macbeth, although he initially dismisses the idea as, "not within the prospect of belief."(74) On reflection, however, he does begin to wonder about the potential of the witches' words and what may lie in store. He acknowledges, if only to the audience, his "black and deep desires."(I.iv.51). Both Macbeth and Lady Macbeth are incredibly ambitious and although Macbeth will later acknowledge his own "vaulting ambition, which o'er leaps itself,"(I.vii.27), this does not stop him from relaying the details of his encounter with the witches to Lady Macbeth so that she can relish "What greatness is promised thee."(I.v.10)
Lady Macbeth, at this stage, is unfailing in her determination and ponders Macbeth's "human kindness," (14) which she sees as a potential stumbling block in his now anticipated rise "to have thee crowned withal."(26) When she learns that Duncan'a arrival is imminent, she steels herself for the "fatal entrance of Duncan" (36). She is now so desperate to ensure Macbeth's succession to the throne that she calls upon the spirits to "unsex me here and fill me...Of direst cruelty." (39-40) It is Lady Macbeth's intention that Duncan should die as is clear from her words: "O, never shall sun that morrow see." (58). She is confident that Macbeth should "leave all the rest to me."(70)
Lady Macbeth is quite prepared to undermine Macbeth, taking advantage of his insecurities by suggesting that he is less of a man if he changes his mind in their plan to eliminate Duncan. She reminds him that, "When you durst do it, then you were a man."(49) Her plan involves Macbeth inviting Duncan to drink with him and, once he and his men are in a drunken stupor and sleeping deeply, she and Macbeth can kill Duncan with his own men's daggers, placing the blame on his own men, ensuring that no one could possibly blame her or Macbeth.
When Duncon arrived in Macbeth's castle then Lady Macbeth plans to kill king Duncon