of violent regime change. Just a year before the play was written, a group of terrorists tried to blow up Parliament and wipe out the entire political establishment, including the king and his family. This incident would still have been fresh in the minds of the play's audience, so Shakespeare played upon it to drive home his message.

It's notable that Macduff's reaction to the discovery of Duncan's murder isn't just one of horror and revulsion, though it is most certainly that. It's also marked by an acknowledgment that this wicked act is an attack upon the natural order of things as ordained by God.

When Macduff refers to this “most sacrilegious murder” having broken open “the Lord's anointed temple” and stolen “the life o' th' building,” he's invoking the Divine Right of Kings, the theory, passionately believed by King James I, that monarchs were directly appointed by God and were answerable to Him alone.

In killing Duncan, then, Macbeth hasn't just committed a very serious crime; he's also committed an act of sacrilege in attempting to subvert the will of God.

Macduff goes to awaken Duncan while Lennox and Macbeth wait outside the door to his chambers. Lennox tells Macbeth about the unnatural weather, with winds so high they knocked down chimneys, as if the earth were delirious with a fever. As an audience, we already know it is Duncan's murder that has caused this weather, which adds to the sense of unease, horror, and foreboding.

When Macduff comes back, having found Duncan's murdered body, he reacts by saying:

O horror, horror, horror!

Tongue nor heart cannot conceive nor name thee!

Macduff discovers Duncan's body in Act II, Scene III. Initially, he is shocked that somebody would commit the murder of a king. For Macduff, the king is anointed and appointed by God: note, for example, how he uses the phrase "God's temple" to describe the king's bedchamber. Consequently, Macduff is outraged by this murder because it is offensive to God.

Macduff is also very upset by the discovery of the body. He tells Macbeth and Lennox that he does not want to talk about the horrible sight he has just witnessed:

Do not bid me speak.

He also refuses to tell Lady Macbeth because he thinks the news is not fit for her ears:

O gentle lady,

'Tis not for you to hear what I can speak.

Finally, for Macduff, the discovery of the body is akin to the end of the world. He calls it "the great doom's image" while he rouses the royal household from their beds. For Macduff, this is a clear act of treason, which he takes extremely seriously.

Macduff is initially annoyed that he's been knocking on the door and Macbeth has taken so long to answer. Macduff is supposed to wake up Duncan, but he has had to wait for Macbeth. Macduff takes his duties to the king seriously because he is loyal.

Upon discovering Duncan's body, Macduff is horrified. At first, he can not even find the words to describe what he has seen. He says "Tongue nor heart / Cannot conceive nor name thee." (II.iii.67) He then finds the words. He says "Confusion hath made his masterpiece." (68) He means that it is a perfect work (masterpiece) of destruction (confusion). He calls the murder sacrilegious because it seems so unholy and because kings were thought to be ordained by God. He tells Macbeth and Lennox that the sight is so horrible, it will turn them to stone. He references the Gorgon (Medusa), a monster so horrible to look at that she would turn one to stone.

Macduff cries out that it is treason and summons Malcolm and Donalbain from their sleep. Macduff is clearly outraged and disgusted. As a loyal subject to the king, he is extremely disheartened. And the sight of Ducnan's murdered boy must be gruesome, given Macduff's horrified reaction.

To answer this question, take a look at Act II, Scene III. It is early morning at Macbeth's castle. Macduff has been instructed by the king to wake him early, so he and Lennox ask Macbeth to take them to Duncan's chamber.

Macduff says that he will wake the king because it is his job ("service"). However, on entering the chamber, Macduff finds King Duncan's bloody corpse. He runs outside to tell Macbeth and Lennox of his grisly discovery:

Most sacrilegious murder hath broke ope

The Lord’s anointed temple, and stole thence

The life o' th' building!

Macbeth and Lennox can hardly believe what Macduff has told them, so they go into the bedchamber to see for themselves. Meanwhile, Macduff rings the bell to wake everyone up and tell them the bad news. Lady Macbeth and Banquo soon arrive and Macduff informs them of what has happened.

Of course, the reader knows that Macbeth and Lady Macbeth already know that Duncan is dead because they are responsible for his murder. But they must keep this quiet if they are to evade detection.

Macduff discovers King Duncan's body. He arrives in the morning after the murder, saying that the king ordered him to call on him at that time. Macbeth leads him to the room, and after a short time, he emerges describing the horror of the scene, which he likens to a "new Gorgon," meaning, like the fabled Medusa, the sight of the King's bloody corpse is so terrible it will "destroy" them. Macduff is clearly shaken by the sight, and Macbeth pretends he does not know what has happened. His wife also feigns ignorance when she arrives from her bedroom, awakened by Macduff's shouting. Macbeth enters the room after Macduff leaves and kills the two guards, who he blames for the murder. Malcolm and Donalbain flee the country, fearing for their own lives. Macduff, the man who discovers the king's dead body, will ultimately be the one who avenges his death.

Well, in Act II scene 3 we see Macbeth in a very difficult position. He of course already knows that Duncan is dead, and yet, to avoid casting suspicion upon himself, he needs to present a credibly shocked response when he is urged by Madcuff to go in to the King's bedchamber and see for himself what has happened to Duncan. What is interesting to think about is how "convinced" we are about Macbeth's performance when he emerges from the bedchamber. Note what he says:

Had I but died an hour before this chance,

I had liv'd a blessed time; for, from this instant,

There's nothing serious in mortality;

All is but toys; renown, and grade, is dead;

The wine of life is drawn, and the mere lees

Is left this vault to brag of.

This speech has something of a rehearsed quality about it and arguably could be considered unrealistic. It is hard to imagine that Macbeth could come up with such eloquence so quickly if he really had been surprised by the death of Duncan. Note too the way that Macduff's response is contrasted with Macbeth's: Macduff is struck almost speechless with horror - he cannot bring himself to even describe what has happened and must send the others in to see for themselves. This juxtaposition adds an extra note of inauthenticity to Macbeth's too-polished words.