The play opens with Macbeth and Banquo, two of the Scottish King Duncan's generals returning from battle when they encounter three witches in the woods. The witches tell Macbeth of how he will become the Thane of Cawdor and then the King of Scotland. For Banquo, they prophesize that he will beget the line of Scottish Kings, though he will never become king himself. The two are sufficiently skeptical and continue their journey home.
However, when the two come closer to the encampment, they are presented with a messenger from King Duncan who announces that Macbeth has been made the Thane of Cawdor, immediately putting the prophecy into perspective, making Macbeth wonder how he might become king. He invites Duncan to dine at his castle that evening and goes ahead to tell his wife of the day's events.
Unlike Macbeth, Lady Macbeth is very sure of her husband's future, desiring the throne and telling him that they must murder Duncan to ensure his ascension. Immediately upon returning to his castle, Lady Macbeth is able to convince her husband to take initiative and murder Duncan that very night.
The two plan to get Duncan's chamberlains drunk enough that they will not remember the evening and blame them for the murder. When the body of Duncan is discovered in the morning, Macbeth quickly kills the "culprits" and assumes the kingship. All the while, Duncan's sons flee the country, afraid for their own lives.
Immediately, Macbeth's misgivings and trust in the prophecies force his hand in the murder of Banquo and his son Fleance as well, afraid that his heirs will seize the throne. Successfully killing Banquo, the murderers fail to kill Fleance.
The night of his murder, Banquo's ghost appears to Macbeth and sends him into hysteria, scaring his guests and angering his wife. His very presence as the king of Scotland has angered the other nobles and further incites Macbeth's misgivings and paranoia.
To ease his fears, he visits the witches again and they offer to him more prophecies. He must beware of Macduff, a chief opponent to Macbeth taking the throne. He cannot be harmed by any man born of woman and he is safe until Birnam Wood comes to Dunsinane Castle. He returns home and finds that Macduff has fled to England to join Malcolm. In fear, Macbeth seizes Macduff's castle and orders the murder of his wife and children, inciting Macduff to further rage. With Malcolm, the two raise an army and ride to Scotland to take on Macbeth with the support of the Scottish nobles who fear Macbeth's tyranny and murderous ways.
While Macbeth awaits his opponents, Lady Macbeth is in the process of going mad, unable to wash the blood from her hands. The news of her suicide reaches Macbeth directly before the arrival of the English forces and sends him into an even deeper despair. He awaits confidently as the prophecy foretold his invulnerability. However, Macduff's forces arrive under the cover of boughs cut from Birnam wood. When Macbeth is finally confronted by Macduff after his forces have been overwhelmed, Macduff announces that he was "ripped from his mother's womb" not born and ultimately defeats and beheads Macbeth, handing the crown back to Malcolm, the rightful heir.