Macbeth prepares for war and visits the three witches to learn what outcome to expect.
Using the blood of a sow who has eaten her young and the sweat that fell from a murderer as he was being hanged, the witches bring forth three apparitions.
The first, an armed head, tells Macbeth to beware of Macduff, the Thane of Fife. This first apparition really shows Macduff beheading Macbeth, but we don’t find this out until Act V.
The second, a bloody child, advises Macbeth that no one who was born of a woman can harm him. Since everyone is born of women, Macbeth figures that he’s in the clear. Nonetheless, to make “double sure,” Macbeth decides to kill Macduff anyway. The second apparition foretells his death, his killer, and his supplanters.
The third, a crowned child with a tree in his hand, tells Macbeth he will never be defeated until Birnam Wood (the forest) around his castle marches toward the castle. The third apparition signals the march from Birnam Wood to Dunsinane and the unnatural giving way to order.
Macbeth still wants one more answer: Will Banquo’s descendants ever rule Scotland? The witches conjure a procession of eight kings, the last of whom holds a mirror that makes it seem as though the line of kings stretches endlessly.
All of the kings in the procession resemble Banquo, and Banquo himself comes behind the line of eight, his hair caked with blood. Macbeth assumes Banquo’s descendants will, in fact, rule Scotland.
To cheer him up, the witches perform a wild dance and disappear. Like so many fictional murderers, Macbeth can’t seem to get out of the habit of killing.
When he learns of Macduff’s flight to England, he seeks revenge by planning a surprise attack on Macduff’s castle at Fife, murdering Macduff’s wife, children, and servants.
Ross meets with Lady Macduff and reassures Lady Macduff that her husband is a wise and trustworthy man. After Ross leaves, the murderers Macbeth has hired for the event break in and slaughter the entire family.
We see how swiftly Macbeth carries out his revenge against Macduff. In England, Malcolm is at first reluctant to side with Macduff.
Malcolm mistrusts Macduff until he tests the degree to which Macduff is loyal to the late Duncan and disloyal to Macbeth.
Malcolm tests Macduff’s loyalty through a set of clever questions; that such a test is necessary shows the extent of Macbeth’s depravity.
Scotland lies in ruins, violence and death commonplace. Macduff passes the test, and together they plan their attack on Scotland.
“How does my wife?” inquires Macduff. “Why, well,” replies Ross.
“And my children?” Macduff asks, to which Ross answers, “Well, too.” Macduff then asks whether Macbeth has harassed his family.
“No,” says Ross, “they were well at peace, when I did leave ‘em.” Of course they were; they were dead.
Finally, Ross tells Macduff that Macbeth has had his wife and children “savagely slaughtered.”
Macbeth’s tyranny is evident, and Macduff realizes that for the good of Scotland, he must be deposed. Meanwhile, Siward is leading an invasion into Scotland.