Macduff, in Shakespeare's Macbeth, is
            caught in the middle of Macbeth's evil scheming to take the throne and keep it. Macduff
            appears first when Duncan has been murdered.
Macduff's
            suspicions may first appear in learning that Macbeth killed the alleged murderers of the
            King (his guards). When Macbeth says he is sorry he killed them, Macduff asks why he did
            it? (They were the only "lead" they had in figuring out who was behind the plot to kill
            Duncan, for the men believe the guards did not act on their
            own.)
            readability="19">
MACBETH:
O,
            yet I do repent me of my fury,
That I did kill
            them.
MACDUFF:
Wherefore
            did you
            so?
MACBETH:
Who
            can be wise, amazed, temperate and furious,
Loyal and
            neutral, in a moment? No man:
The expedition of my violent
            love
Outrun the pauser reason.
            (II.iii.117-123)
Along with
            the others, Macduff calls for an investigation—the King's murderer
            must be found.
Macduff is also
            seemingly suspicious when he and Ross discuss the burial of Duncan and Macbeth's
            crowning as King, as Malcolm and Donalbain have fled (for safety, though certainly
            Macbeth is spreading the rumor that they are behind their father's death—he will
            eventually refer to them as his "blood cousins").
There may
            be an inkling of doubt when Macduff repeats once again that the guards were murdered by
            Macbeth. He then takes his leave of Ross, noting that he hopes they do not soon wish for
            the days when Duncan was alive as opposed to being Macbeth's subjects (as he refers to
            robes):
            readability="10">
MACDUFF:
Well,
            may you see things well done there, Adieu,
Lest our old
            robes sit easier than our new!
            (II.iv.49-50)
However,
            everyone (including Macduff) soon comes to realize that those closest to Macbeth end up
            dead. The Scotland of Duncan's time is gone. Macduff's suspicions grow, so he goes to
            England.
When Macduff leaves Scotland for the country where
            Malcolm (Duncan's heir) is living for safety's sake, even Malcolm questions Macduff's
            intentions for being there. For how could an honest man feel he could comfortably leave
            his family behind without threat from Macbeth unless Macduff were working for
            Macbeth?
In his desire to save Scotland (similar to Brutus'
            desire to preserve Rome at all costs when he murders Caesar in Shakespeare's
            Julius Caesar), Macduff acts foolishly by leaving his family
            unguarded. When Macbeth learns about Macduff's departure to England (where Macbeth's
            enemy, Malcolm, resides), he is sure that Macduff has taken up with Duncan's son, and
            orders the murder of all of Macduff's family and
            household.
Macduff's devastation over their deaths—along
            with his initial disgust when he believes Malcolm would be a far worse tyrant on
            Scotland's throne than Macbeth (which he later learns is untrue)— convinces Malcolm that
            Macduff can be trusted. With soldiers and arms provided by Edward the Confessor of
            England, Malcolm and Macduff return to Scotland to take the throne forcibly from
            Macbeth.
So Macduff facilitates Macbeth's continued evil in
            leaving his family unattended, allowing the new and evil King to kill Macduff's wife and
            children; at the same time, however, he prevents further evil by returning with Malcolm
            to take Scotland back. It is, in fact, Macduff who kills Macbeth specifically with the
            intent of avenging the deaths of those dear to him.
            readability="15">
MACDUFF:
Then
            yield thee, coward,
And live to be the show and gaze o’ the
            time.
We'll have thee, as our rarer monsters
            are,
Painted upon a pole, and
            underwrit,
“Here may you see the tyrant.”
            (V.viii.27-31)