In this act, the readers witness how a physician and a nurse find out about some dark stuff that they are not supposed to know about Lady Macbeth. Everyday Lady Macbeth goes to a box picks up a letter seal it and then she goes back to bed. The nurse was suspicious so she asked a physicist to watch, and then Lady Macbeth starts talking about death and blood and Banquo’s death, the nurse and the physicist were scared, so they decided to act if they have not seen nor heard anything.

LADY MACBETH

Out, damned spot! Out, I say!—One, two. Why, then, ’tis time to do ’t. Hell is murky!—Fie, my lord, fie! A soldier, and afeard? What need we fear who knows it, when none can call our power to account?—Yet who would have thought the old man to have had so much blood in him.
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LADY MACBETH

The thane of Fife had a wife. Where is she now?—What, will these hands ne’er be clean?—No more o’ that, my lord, no more o’ that. You mar all with this starting.
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LADY MACBETH

Here’s the smell of the blood still. All the perfumes of Arabia will not sweeten this little hand. Oh, Oh, Oh!
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LADY MACBETH

Wash your hands. Put on your nightgown. Look not so pale.—I tell you yet again, Banquo’s buried; he cannot come out on ’s grave.
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LADY MACBETH

To bed, to bed. There’s knocking at the gate. Come, come, come, come. Give me your hand. What’s done cannot be undone.—To bed, to bed, to bed!