In England, near the palace of King Edward, Macduff urges Malcolm to quickly raise an army against Macbeth. But Malcolm says Macduff might actually be working for Macbeth, a suspicion heightened by the fact that Macduff left his family behind and unprotected in Scotland.
Why does Macduff leave his family behind when he goes to England? Does he underestimate Macbeth's depravity, or has he put too much emphasis on country at the expense of family?
Malcolm then adds that he delays attacking Macbeth because he fears that he himself would perhaps be even a worse ruler. Malcolm describes himself as so lustful, vicious, and greedy that he makes Macbeth look kind. Macduff cries out in horror, and says he will leave Scotland forever since there is no man fit to rule it. Malcolm then reveals that none of his self-description was true: it was a trick to test Macduff's loyalty. Malcolm now believes that Macduff is loyal to Scotland and not Macbeth, and that he has an army of ten thousand men commanded by the English Lord Siward, ready to invade Scotland.
Macduff proves that his morality and love of country is greater than his ambition.
Just then an English doctor enters. Malcolm speaks with the doctor, then tells Macduff that King Edward of England is so saintly that he can cure disease.
In contrast to Macbeth, Edward is so virtuous his touch restores order to nature: it heals.
Ross enters. He tells Malcolm that if he invaded the Scottish people would line up to join his army against Macbeth. Finally, Ross tells Macduff his family has been murdered. Macduff cries out in anguish. Malcolm tells him to fight it like a man. Macduff responds that he must also "feel it like a man" (4.3.223). But they agree that Macduff's anger and grief should be used to fuel his revenge.
True manhood, Macduff realizes in his moment of anguish, involves not just strength, honor, and loyalty, but also emotion, feeling, and love.