Act 1

The play opens on a Scottish heath, where three witches gather in stormy weather. They plan to meet the eponymous but as yet unknown Macbeth after a battle, setting a tone of mystery and supernatural influence [1.1].

Meanwhile, King Duncan receives news that the same Macbeth, a noble and valiant general, has defeated both the rebellious Macdonwald and the invading Norwegians. Impressed, Duncan rewards Macbeth with the title of Thane of Cawdor, an ironic piece of foreshadowing, given that the previous thane was a traitor and Macbeth is destined to be a traitor too [1.2].

As Macbeth and his friend Banquo return from battle, they encounter the witches, who greet Macbeth with three titles, "All hail, Macbeth! Hail to thee, Thane of Glamis! / Hail to thee, Thane of Cawdor! / Hail to thee, that shalt be king hereafter!", of which only the first (Thane of Glamis) is accurate [1.3]. They also predict that Banquo’s descendants will be kings, though he himself will not rule. Shortly after, messengers arrive to confirm Macbeth’s new title of Thane of Cawdor, making him wonder if the prophecy of kingship will also come true.

Lady Macbeth, upon hearing of the prophecy by letter, immediately plots Duncan’s murder. She manipulates Macbeth, questioning his courage and masculinity: "When you durst do it, then you were a man" [1.7]. Macbeth hesitates but is eventually persuaded, deciding to commit regicide (murder of a king/queen) that night.

Act 2

Macbeth sees a vision of a dagger leading him towards Duncan’s chamber: "Is this a dagger which I see before me, / The handle toward my hand?" [2.1]. This hallucination reveals his disturbed mind, and also explores his feelings of apprehension and guilt. He goes on to kill Duncan in his sleep and returns, shaken, with bloodied hands. Lady Macbeth chastises him for failing to take the full plan to completion and takes control, placing the daggers with the sleeping guards and smearing them with blood – a crucial part of the plan, as doing so will frame the guards as murderers.

The next morning, Macduff, a nobleman, discovers the murder [2.3]. Macbeth kills the guards in supposed fury over their crime (in reality, he is ensuring that they die as suspects, rather than living on and proving their innocence), but suspicion lingers. Duncan’s sons, Malcolm and Donalbain, flee to England and Ireland respectively, fearing for their lives. Their flight is convenient for Macbeth’s purposes as it makes them seem guilty of their father’s murder, allowing Macbeth to seize the throne. Macbeth is now king, as the witches predicted (the second prophecy that has come true so far).

Act 3

Now king, Macbeth feels insecure about the witches’ prediction that Banquo’s heirs will rule. Thinking that the survival of his friend and bloodline is a threat to his own power, he hires assassins to kill Banquo and his son, Fleance [3.1]. They succeed in murdering Banquo, but Fleance escapes, leaving Macbeth fearful.

At a banquet that night, Macbeth is horrified when he sees Banquo’s ghost sitting in his seat, and he loudly confronts the ghost in front of his guests [3.4]. No one else can see the ghost of Banquo, of course, and his public outburst unnerves the guests. Lady Macbeth dismisses it as a mere illness of the mind to the guests, but Macbeth realises he must act more ruthlessly to maintain his power.

Meanwhile, Macduff has travelled to England to seek help from Malcolm, Duncan’s son, who fled there after his father’s murder [3.6].

Act 4

Macbeth remains deeply insecure in his position as uncontested king, and so he revisits the witches, demanding answers. They show him three apparitions:

1. An armed head, warning him to beware Macduff, Thane of Fife.

2. A bloody child, assuring him that "none of woman born shall harm Macbeth" [4.1].

3. A crowned child with a tree, promising he is safe until Birnam Wood (the forest adjacent to his castle) moves to Dunsinane (the castle itself).

Feeling invincible in the wake of the second prophecy, but insecure in the face of the first, Macbeth orders the murder of Macduff’s wife and children [4.2]. Meanwhile, in England, Malcolm tests Macduff’s loyalty before revealing that he has an army ready to reclaim Scotland [4.3].

Lady Macbeth, consumed by guilt, begins sleepwalking and obsessively washing her hands, crying "Out, damned spot! Out, I say!" – an unsubtle reference to the concept of guilt as blood on one’s hands [5.1]. Her once-unshakable confidence has crumbled.

Malcolm’s army advances, and they cut down branches from Birnam Wood to disguise their numbers – partially fulfilling the prophecy of Birnam Wood advancing on Dunsinane as they approach the castle under cover of dismembered trees [5.4]. Macbeth clings to the witches’ words, still believing he cannot be harmed by anyone born of woman – which, in his eyes, is anyone.

Lady Macbeth dies offstage, possibly by suicide, and Macbeth’s reaction is understated but devastated, with his tragic "Tomorrow and tomorrow and tomorrow" soliloquy about the futility of life in her absence [5.5]. Then, when he hears Birnam Wood is moving toward the castle, he realises he has been bested.

In the final battle, Macbeth fights bravely but meets Macduff, who reveals he was "from his mother's womb untimely ripp'd" [5.8] – a caesarean birth, meaning he was not "born of woman" in the usual sense. This is known as a quibble: a plot device used to fulfill the exact verbal conditions of an agreement in order to avoid the intended meaning. Macbeth understands his fate is sealed but fights on until Macduff kills him.

Malcolm is declared king, promising to restore order to Scotland. The play ends with a sense of justice being restored, though the brutal consequences of unchecked ambition linger. The unmentioned continued existence of Banquo’s son, Fleance, is a nod to the potential fulfilment of the remaining prophecy (that Banquo’s line will give rise to kings), and a certain nod to King James VI/I, who believed himself to be a descendant of the real-life Banquo of history.