In Macbeth Act III, scene 2 there is a division of labor in the Macbeth marriage. Earlier, in Act I, the two conspired to kill Duncan and his servants. They conspired at night to stage a bloody coup. The next morning, after the body was discovered, they appeared to be like the "innocent flower," but were really the "snake under it." Together, they were clever, cruel, and Machiavellian.
In Act III, however, Macbeth, now as king, plots alone. He tells his wife to be "innocent of the knowledge" of his murderous plot to kill Banquo and Fleance (and later the Macduffs). Macbeth is the one acting like the serpent, and he wants his wife to be the flower. He wants to surprise her with two more murders later, but since she has been suffering from the mental side-effects of the first one, he spares her the details.
This shows that the taste for blood and the power of the crown have gone to Macbeth's head. He says that his "mind is full of scorpions." The imagination of the supernatural that the witches have open his mind to has completely consumed Macbeth. Since Lady Macbeth was never exposed to their supernatural prophecies or the act of killing Duncan, Macbeth takes the reigns of both the unnatural and the supernatural, leaving his wife to wash her hands and sleepwalk.
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As in the earlier scenes, Macbeth reveals everything to Ladymacbeth, but here, Macbeth keeps secret from his wife the plot to murder Banquo. He also alarms her by conjuring up an atmosphere of evil. In the earlier scenes, Lady Macbeth was very ambitious and brave, but here, we hear that she begins to show signs of stress and Macbeth suffers 'terrible dreams'.