Set in medieval Scotland and partly based on a true historical account, Macbeth charts the bloody rise to power and tragic downfall of the warrior Macbeth. Already a successful soldier in the army of King Duncan, Macbeth is informed by Three Witches that he is to become king. As part of the same prophecy, the Witches predict that future Scottish kings will be descended not from Macbeth but from his fellow army captain, Banquo. Although initially prepared to wait for Fate to take its course, Macbeth is stung by ambition and confusion when King Duncan nominates his son Malcolm as his heir.
Returning to his castle, Macbeth allows himself to be persuaded and directed by his ambitious wife, who realizes that regicide — the murder of the king — is the quickest way to achieve the destiny that her husband has been promised. A perfect opportunity presents itself when King Duncan pays a royal visit to Macbeth's castle. At first Macbeth is loth to commit a crime that he knows will invite judgment, if not on earth then in heaven. Once more, however, his wife prevails upon him. Following an evening of revelry, Lady Macbeth drugs the guards of the king's bedchamber; then, at a given signal, Macbeth, although filled with misgivings, ascends to the king's room and murders him while he sleeps. Haunted by what he has done, Macbeth is once more reprimanded by his wife, whose inner strength seems only to have been increased by the treacherous killing. Suddenly, both are alarmed by a loud knocking at the castle door.
When the drunken porter of Macbeth's castle finally responds to the noise, he opens the door to Macduff, a loyal follower of the king, who has been asked to awake Duncan in preparation for the return journey. Macbeth indicates the location of the king's room, and Macduff discovers the body. When the murder is revealed, Macbeth swiftly kills the prime witnesses, the sleepy guards of the king's bedchamber, and Lady Macbeth faints. The assembled lords of Scotland, including Macbeth, swear to avenge the murder. With suspicion heavy in the air, the king's two sons flee the country: Donalbain to Ireland and Malcolm to raise an army in England.
Macbeth is duly proclaimed the new king of Scotland, but recalling the Witches' second prophecy, he arranges the murder of his fellow soldier Banquo and his son Fleance, both of whom represent a threat to his kingship according to the Witches' prophecy. The hired murderers kill Banquo but mistakenly allow Fleance to escape. At a celebratory banquet that night, Macbeth is thrown into a state of horror when the ghost of the murdered Banquo appears at the dining table. Again, his wife tries to strengthen Macbeth, but the strain is clearly beginning to show.
The following day, Macbeth returns to the same Witches who initially foretold his destiny. This time, the Witches not only confirm that the sons of Banquo will rule in Scotland, but they also add a new prophecy: Macbeth will be invincible in battle until the time when the forest of Birnam moves towards his stronghold at Dunsinane and until he meets an enemy "not born of woman." Dismissing both of these predictions as nonsense, Macbeth prepares for invasion.
When he is told that Macduff has deserted him, Macbeth begins the final stage of his tragic descent. His first move is the destruction of Macduff's wife and children. In England, Macduff receives the news at the very moment that he swears his allegiance to the young Malcolm. Malcolm persuades him that the murder of his family should act as the spur to revenge.
Meanwhile, in Scotland, Lady Macbeth has been taken ill: She walks in her sleep and seems to recall, in fragmentary memories, the details of the murder. Now, in a series of alternating scenes, the action of the play moves rapidly between the advancing army of Malcolm and the defensive preparations of Macbeth. When Malcolm's army disguise themselves with sawn-off branches, Macbeth sees what appears to be a wood moving towards his stronghold at Dunsinane. And when he finally meets Macduff in single combat, his sworn enemy reveals that he came into the world by cesarean section; he was not, precisely speaking, "born of woman." On hearing this news, Macbeth rejects one final time the Witches' prophecy. With a loud cry, he launches himself at Macduff and is slain. In the final scene, Malcolm is crowned as the new king of Scotland, to the acclaim of all.