Scene 1: Three witches plan to meet Macbeth on a Scottish moor.
Scene 2: King Duncan receives news of Macbeth and Banquo's heroic deeds on the battlefield. He learns the rebellious thane of Cawdor has been defeated. Duncan announces Macbeth will be named the new thane of Cawdor.
Scene 3: Macbeth approaches the three witches who hail him as thane of Glamis (his known title) and thane of Cawdor (unknown to Macbeth). The witches proclaim that Macbeth will be crowned king and that Banquo's descendants will gain the throne. Ross and Angus arrive and inform Macbeth, already in deep thought over the witches' prophecy, he has been named thane of Cawdor. Macbeth wonders whether the throne will come to him through natural events or if he must commit dark deeds to obtain it.
Scene 4: Duncan announces Malcolm as the heir to his throne. Macbeth immediately considers Malcolm an obstacle. Duncan plans to dine at Macbeth's castle that evening. Macbeth leaves early to inform his wife and prepare for the king's arrival.
Scene 5: Lady Macbeth reads aloud a letter from her husband. She fears, however, that Macbeth's ambition is too much tempered by his kindness. She resolves, therefore, to convince her husband to follow his ambition and puts her femine gentleness aside and vows to have Duncan killed before he leaves Inverness (Macbeth's castle).
Scene 6: Duncan arrives and praises Macbeth and Lady Macbeth.
Scene 7: Macbeth ponders the situation but finds no reason to slay the king other than his own ambition, which undoubtedly will bring unforetold evils upon himself. Macbeth informs his wife that he has changed his mind about assassinating the king. Lady Macbeth chastises her husband for his weakness.
Brief Analysis: The play's beginning forebodes ill and establishes a dark mood for the entire play. Act I is full of contrasts where "fair is foul and foul is fair," none more glaring than Macbeth, who is brave and loyal on the battlefield and ambitious and disloyal off it. Macbeth's decision, influenced greatly by his wife, to kill Duncan violates three principles:
(1) Duncan is a benevolent and good king;
(2) Macbeth is a subject to the king and has vowed loyalty;
(3) Duncan is a guest in Macbeth's home and is, therefore, accorded the rights of hospitality.