In Macbeth, Macbeth and Lady Macbeth are intent on realizing the witches' prophesies, wherein Macbeth will be king. The witches maintain: "All hail, Macbeth, that shalt be king hereafter!" (I.iii.50) Macbeth has been unable to think of little else and has been contemplating, what he calls "that suggestion Whose horrid image doth unfix my hair."(135) He gives a brief thought to the possibility of becoming king "without my stir," (143) but, once Lady Macbeth's determination persuades him that he must go ahead with Duncan's murder or else, "live a coward in thine own esteem," (I.vii.43) he takes matters much further than he or Lady Macbeth ever contemplated or conceived.
At first, Lady Macbeth, determined to be the wife of the king, even calls on the spirits to "unsex me here" (I.v.38) to ensure that she remains resolute in her intentions. She believes that killing Duncan will suffice and that her plan will be perfect as other men - Duncan's "spongy officers," (I.vii.71)- will be blamed and she and Macbeth will be free to enjoy their ill-gotten reward, any guilt simply washed away because, as she says: "A little water clears us of this deed."(II.ii.67)
Matters do not proceed as Lady Macbeth may have hoped and she is aware of the change in Macbeth. Her happiness is marred by his preoccupation and "Naught's had, all's spent, Where our desire is got without content," (III.ii.4-5) indicates how, although they have achieved their "desire," and there is nothing more that they can do to ensure their happiness, they are not happy. She reminds Macbeth that, "What's done is done," (12) and urges him to let it go but he is worried that his position is not secure as the witches also promised that Banquo's sons would be king, making him believe that, "We have scotch'd the snake, not killed it."(13) Lady Macbeth's words then foreshadow what will follow as she will ultimately be driven mad by her guilt as Macbeth takes matters into his own hands and proceeds to kill anyone that he perceives to be a threat.