After his first meeting with the weird sisters, Macbeth was worried that he would be forced to commit murder in order to gain the Scottish crown. Since then, he seems to have become accustomed to the idea, as the body count has rapidly grown. The first part of the witches' prophecy having already been realized, Macbeth fears that the second part may become true. He thinks that he must have his friend Banquo and his son eliminated in order to prevent such an occurrence. However, as Fleance's survival implies, there is no escape from the witches' prophecies.
In this act, Macbeth seems to have assumed the role of Lady Macbeth. As he speaks to the murderers, Macbeth makes takes advantage of the same expression that Lady Macbeth used to convince him to murder Duncan in Act I, scene vii. He questions their manhood in order to anger them, thus raising their desire to murder Banquo and Fleance to prove that they are, in fact, men.
In the following scene, Macbeth once more repeats his wife's previous comments. Lady Macbeth had earlier mentioned to him that he must "look like the innocent flower, / But be the serpent under't" (I.v.64-65). Now, the tables seem to have turned, and we find Macbeth reminding his wife to disguise her discomfort, as he states that they must "make [their] faces vizards to [their] hearts, / Disguising what they are" (III.ii.35-36). However, in spite of his demonstrations of courage, Macbeth is irrefutably overwhelmed by guilt and doubt. He conveys these feelings in his reference to the "scorpions" in his mind, and in declaring that by killing Banquo they "have scorched the snake, not killed it" (III.ii.13).
As her husband grows bolder, Lady Macbeth begins to despair. It is quite hard to believe that the...