After receiving Macbeth's letter regarding the witches' favorable prophecies, Lady Macbeth calls upon evil spirits to consume her soul and fill her with cruelty in order to help assassinate King Duncan. In act five, scene one, Lady Macbeth tells her husband that she will make preparations for the murder and says, "Leave all the rest to me" (Shakespeare, 1.5.65). Lady Macbeth's comment is meaningful and emphasizes her significant role in King Duncan's murder. Lady Macbeth not only ridicules her husband for acting like a coward but also plans and orchestrates the entire assassination. Lady Macbeth drugs Duncan's chamberlains before Macbeth enters the king's room in order to prevent them from interfering. Following the murder, Lady Macbeth returns the bloody daggers and smears Duncan's blood onto the deceased chamberlains, which makes it look like they assassinated the king.

Lady Macbeth not only influences her husband to follow through with the murder but also plots and executes the crime by drugging the chamberlains and strategically placing the daggers back into the room. One could argue that without Lady Macbeth's influence and scheme, her husband would not have followed through with the assassination. Since Macbeth's crime only leads to more bloody murders and subsequently results in her paranoia, it is fair to say that Lady Macbeth and her husband's demise is a direct result of her influence, planning, and execution.