The Three Witches are preparing a spell to cast on Macbeth at the beginning.
The witches show Macbeth an armed head that tells him to beware of Macduff, a bloody child that tells he cannot be defeated by anyone born of a woman and a crowned child holding a tree tells him that he will not be defeated until the woods move. Macbeth also asks about Banquo's future and is shown a line of never ending kings.
Lennox informs Macbeth that Macduff has joined Malcolm in England. This makes Macbeth angry and he decides to attack Macduff's castle and kill everyone in it.
Lady Macduff is unhappy with her husband for abandoning them. After a brief conversation between Lady Macduff and her son, Macbeth kills everyone in Macduff's castle.
Macduff is trying to convince Malcolm to attack Scotland and to take his title back from Macbeth. Malcolm denies Macduff's wishes saying that he is not fit to be a king because he is greedy and will spend all his time chasing women. He could be worse than Macbeth.
Macduff gets angry at Malcolm and Malcolm reveals that he was lying to test Macduff's loyalty. Ross arrives in England and informs Macduff of the tragedy that has happened at his castle.