Macbeth continues his descent into paranoia and tyranny. He has Banquo murdered at a feast, but Fleance escapes. Macbeth sees Banquo's ghost and grows more distrustful. The witches prophesy that Macbeth will not be defeated until Birnam Wood comes to Dunsinane Castle. Lady Macduff and her son are murdered on Macbeth's orders. Macduff flees to England to join Malcolm in plotting an invasion to defeat Macbeth and restore order to Scotland.