At Fife (Macduff's castle), Lady Macduff is angry. She demands to know why Macduff has gone to England, leaving her behind. She thinks Macduff is a coward. Ross says Macduff's flight could results from wisdom, not fear.
Another debate about manhood. Does a real man sacrifice the safety of his family for the good of his country?
After Ross leaves, Lady Macduff turns to her son. She tells the boy that his father is dead. The boy doesn't believe her, but asks if his father is a traitor. Lady Macduff says yes, Macduff is a traitor: a man who swore an oath and broke it and now must hang. The boy thinks if traitors allow themselves to be hanged they must be fools, since there are undoubtedly more traitors than honest men in the world.
Macduff's son is wise beyond his years, noting that those who put themselves above society far outnumber those who put the common good above their own selfish ambitions.
A servant bursts in to warn of coming danger, then rushes out. Before Lady Macduff or her children can run, murderers enter the chamber, stab Macduff's son, and chase Lady Macduff offstage.
Macbeth has ordered the murder of the innocent. His loss of humanity is complete, and the seeds of his self-destruction are sown.