In Act I of Shakespeare's Macbeth, Lady Macbeth first appears as she reads a letter from her warrior husband. Much like the ruthless spectator, she remarks upon Macbeth's message with apprehensions about her husband even though he has proven himself recently in battle,
Yet do I fear thy nature;
It is too full o’ the milk of human kindness
To catch the nearest way. Thou wouldst be great;
Art not without ambition, but without
The illness should attend it. What thou wouldst highly,
That wouldst thou holily; wouldst not play false,
And yet wouldst wrongly win. (1.5.14-20)
Interestingly, Lady Macbeth, in her inactive role, believes that she can "pour [her] spirits" in his ear and with the "valor" of her tongue provide Macbeth with the sang froid he needs to carry out the acts necessary for his becoming king.
Then, in Scene 7, Lady Macbeth's words make a connection between masculinity and violence, a connection that seems to play out later in the drama as she clearly proves the "weaker sex." Summoning the spirits, she asks that she be unsexed and filled with "direst cruelty." However, when the time comes for Macbeth to murder King Duncan, Lady Macbeth's "direst cruelty" wanes as she cannot commit the heinous deed because Duncan "resembled/My father as he slept" (2.2.15-16).
Later, in Act 5, Scene 1, Lady Macbeth proves that her courage has been, indeed, only that of the spectator and not the actor that she has believed she would be in the spectacle of violence. For, Lady Macbeth's agonizing guilt has caused her to lose her touch with reality as she imagines blood on her hands and guards coming for her,
The Thane of Fife had a wife; where is she
now? What, will these hands ne'er be clean? No more o’
that, my lord, no more o’ that. You mar all with this(40)
To bed, to bed; there's knocking at the gate.
Come, come, come, come, give me your hand. What's
done cannot be undone. To bed, to bed, to bed. (5.1.60-62)
Ironically, however, Lady Macbeth becomes more human in her mental decline from a guilt-ridden conscience. Certainly, she returns to the woman that she has been before becoming the "desexed" heartless villain of the first part of the play.