Why does Macbeth forget to take the daggers from the guards?
In Act II, scene ii., Macbeth reports to his wife that the foul crime is done, that Duncan is slain while his guards lay in a drug-induced sleep. Shaken by the experience, Macbeth's account is interrupted by Lady Macbeth as she spies the daggers in his hand that were meant to be left by the sides of the guards, thereby implicating them in the crime. When she directs him to go back and lay the daggers by the guards, he refuses, saying that he fears to look upon the aftermath of his bloody deed. She blurts out, "Infirm of purpose! Give me the daggers" (II, ii., 49-50). Macbeth's failure to carry out his wife's instructions about the daggers performs a key function. By undertaking the errand herself, Lady Macbeth physically soils her hands with the king's blood. Not only does this provide a basis for her incessant washing of the "spots" on her hands, it takes Lady Macbeth further into the execution of the crime than she is prepared to go. We recall her assertion that she would have killed Duncan herself had he not resembled her own father in his sleep. Yet her behavior after Duncan's death casts doubt upon this claim. Paradoxically, the dagger ruse proves unnecessary, for the Scottish court places the blame for Duncan's murder on his sons. Neither Lady Macbeth nor her husband is able to act with perfectly deliberate calculation.