Macbeth, the powerful Thane of Glamis, has led the Scottish army of King Duncan to victory against an invading force and has personally fought bravely. As he returns from the battle with his best friend, Banquo, they meet three Witches. They predict that Macbeth will be made Thane of Cawdor (a more powerful position than that he currently holds) and eventually become King of Scotland. They also tell Banquo that although he will never be king, his descendants will; the Witches then vanish. Almost immediately, Macbeth receives the news that in gratitude for leading his troops to victory Duncan is making him Thane of Cawdor. Macbeth begins to wonder whether this means the other predictions will come true as well.
Duncan is due to stay with the Macbeths as a house guest. When Lady Macbeth receives Macbeth's news in a letter, she resolves to make the most of the situation. Macbeth and his wife plan and carry out Duncan's murder. When Macbeth hesitates, his wife encourages him; she even takes part in the action. They try to cover up their deed by making it seem as if the King's servants are responsible. The following morning, Macduff, the Thane of Fife, discovers the King's body. In the confusion that follows, Macbeth kills Duncan's innocent guards so that they cannot talk. Malcolm and Donalbain, the king's sons, flee the country and the way is left clear for Macbeth to seize the throne.