The play is set primarily in Scotland, and follows the character of Macbeth, a bold Scottish general, as he becomes power-hungry and demented with political ambition. Shakespeare brilliantly portrays Macbeth and Lady Macbeth's downward spiral as they struggle with the punishing physical and psychological effects of greed.
The first act begins during a wild thunderstorm, as three witches decide they shall next meet with Macbeth, a general praised for his bravery from the Scottish army. The witches tell Macbeth and his fellow general and friend Banquo their prophecies about the men's future. Their responses seem to indicate that Macbeth will become first a "Thame of Glamis" and a "Thame of Cawdor," and then shall become "King hereafter."
Leaving the two men questioning to cryptic prophecies, the thane Ross arrives upon the scene and informs Macbeth that he is now the Thane of Cawdor, as the previous thane has been put to death for treason. With the witches' first prophecy fulfilled, Macbeth, at first skeptical, begins to imagine himself as inheriting the throne.
Macbeth and Banquo are welcomed by King Duncan, and he praises them for their valor in battle and announces that he would like to spend the night at Macbeth's castle. King Duncan also announces that his son, Malcolm, will be his heir, which Macbeth feels further necessitates his speedy action to steal the throne. Writing ahead to his wife, Macbeth confesses the story about the witches' prophecies. Lady Macbeth, with an unscrupulous greed for the throne, challenges her husband's manhood for his reticence in killing the king, and persuades him to kill King Duncan that very night. They plan on intoxicating the King's chamberlains and then framing them for the murder.
Act two begins with Macbeth, still questioning himself, stabs King Duncan. He is so disturbed by his own actions that Lady Macbeth takes charge of framing the servants. The next morning, when Duncan's body is discovered, his sons flee, fearing that they are also in danger. Their flight makes them suspects as Macbeth assumes the throne. Banquo, remembering the witches prophecy, becomes suspicious of Macbeth's ascension.
Macbeth's internal turmoil grows and he orders his friend Banquo killed. Banquo's ghost then haunts him. Guests watching Macbeth raving at an empty chair that holds the ghost of Banquo only he can see fear Macbeth has gone insane, but Lady Macbeth convinces them otherwise. However, Macbeth is indeed descending into madness and he goes again to visit the three witches for answers to his questions about the prophecies. They produce horrific apparitions yet assure him he is safe from danger. Perhaps buoyed by a sense of security, Macbeth commits another horrific act and orders the murder of Macduff, the nobleman who discovered Duncan dead. Since Macduff has fled to England, Macbeth orders his entire family killed.
Lady Macbeth's conscience catches up to her husband and she becomes sick with guilt, hallucinating bloodstains on her hands. She commits suicide in her madness, the news of which sends Macbeth into a deep despair. Macduff, hearing of his family's murder, vows revenge. Together with Duncan's son Malcolm and an army, they ride back to Scotland. Macbeth, too confident of his own power, is struck down and beheaded by Macduff, and Malcolm inherits his rightful throne.