Lady Macbeth is one of Shakespeare's most famous and frightening female characters. When we first see her, she is already plotting Duncan's murder, and she is stronger, more ruthless, and more ambitious than her husband. She seems fully aware of this and knows that she will have to push Macbeth into committing murder. At one point, she wishes that she were not a woman so that she could do it herself. This theme of the relationship between gender and power is key to Lady Macbeth's character: her husband implies that she is a masculine soul inhabiting a female body, which seems to link masculinity to ambition and violence. Shakespeare, however, seems to use her, and the witches, to undercut Macbeth's idea that "undaunted mettle should compose / Nothing but males" (1.7.73–74). These crafty women use female methods of achieving power—that is, manipulation—to further their supposedly male ambitions. Women, the play implies, can be as ambitious and cruel as men, yet social constraints deny them the means to pursue these ambitions on their own.
Lady Macbeth manipulates her husband with remarkable effectiveness, overriding all his objections; when he hesitates to murder, she repeatedly questions his manhood until he feels that he must commit murder to prove himself. Lady Macbeth's remarkable strength of will persists through the murder of the king—it is she who steadies her husband's nerves immediately after the crime has been perpetrated. Afterward, however, she begins a slow slide into madness—just as ambition affects her more strongly than Macbeth before the crime, so does guilt plague her more strongly afterward. By the close of the play, she has been reduced to sleepwalking through the castle, desperately trying to wash away an invisible bloodstain. Once the sense of guilt comes home to roost, Lady Macbeth's sensitivity becomes a weakness, and she is unable to cope. Significantly, she (apparently) kills herself, signaling her total inability to deal with the legacy of their crimes.
