Three witches meet Macbeth and Banquo on the heath as the men return from battle. They predict that Macbeth will be named Thane of Cawdor and King of Scotland and that Banquo will be the father of kings. The witches vanish; Ross enters to greet Macbeth with the title of Cawdor, the traitor whom King Duncan has determined must be executed and whose title and lands will be given to Macbeth. This immediate “earnest of success commencing in a truth” causes Macbeth to consider the extent of his ambition and Banquo to warn that predictions are often harmful as well as beneficial. (iii.) Announcing that his eldest son, Malcolm, is to be his heir, Duncan states his intention to visit Macbeth’s castle, Glamis. (iv.)
When Lady Macbeth reads the letter Macbeth has sent ahead, she determines her husband must take advantage of the opportunity Duncan’s forthcoming visit offers as a way of fulfilling the prophecy. However, she fears that though Macbeth is “not without ambition,” he is “too full o’ th’ milk of human kindness to catch the nearest way.” (v.) Macbeth is not as determined as his lady about the need for murder. He considers reasons he should defend rather than threaten the life of his king. Lady Macbeth remains adamant and pressures him with attacks on his manhood as well as reminders of their feelings for each other. She convinces Macbeth to proceed by presenting her plan to drug Duncan’s guards and leave evidence that will implicate them in the crime. (vii.)