Act III scene iv of Hamlet by William Shakespeare takes place in Gertrude's chamber (bedroom), and it is safe to say that Hamlet is not happy. Though his father's ghost has asked him not to deal too harshly with Gertrude, Hamlet has been called into her room and takes advantage of this time alone with her (well, except for Polonius hiding, once again, behind a tapestry) to express his disgust at her behavior.
He enters the room angry and frustrated (he has just come from an opportunity to kill Claudius but chose to wait because he seemed to be at confession) and immediately hurls insults at his mother, including wishing that she were not his mother. When he hears someone behind the tapestry, he is ready to do some damage. More than ready, in fact. He stabs Polonius, thinking it is Claudius. Though he feels some regret for his action, he blames Polonius for being where he should not have been, a habit the man had, it seems.
Certainly Gertrude is shaken both by the act of murder so close to her but also by the anger she sees in her son. The source of his anger, of course, is her "o'erhasty marriage" to her brother-in-law Claudius, and he is about to make sure she knows exactly how he feels about what she has done. Hamlet goes straight to the heart of his frustrations when he forces Gertrude to look at two pictures, one of his father and one of Claudius.
Look here, upon this picture, and on this,
The counterfeit presentment of two brothers.
See, what a grace was seated on this brow;
Hyperion's curls; the front of Jove himself;
An eye like Mars, to threaten and command;
A station like the herald Mercury
New-lighted on a heaven-kissing hill;
A combination and a form indeed,
Where every god did seem to set his seal,
To give the world assurance of a man:
This was your husband. Look you now, what follows:
Here is your husband; like a mildew'd ear,
Blasting his wholesome brother. Have you eyes?
Could you on this fair mountain leave to feed,
And batten on this moor? Ha! have you eyes?
You cannot call it love; for at your age
The hey-day in the blood is tame, it's humble,
And waits upon the judgment: and what judgment
Would step from this to this?
He scolds Gertrude for her lack of virtue, for her seeming lack of wisdom and discernment, and for her lack of shame. He is unrelenting and unmerciful; even as she begs him to stop his tirade of accusations, Hamlet continues. Only the presence of his father's ghost tempers his anger. When she asks what she can do to make things right, he tells her:
Confess yourself to heaven;
Repent what's past; avoid what is to come;
And do not spread the compost on the weeds,
To make them ranker.
During this scene, Hamlet is finally able to express what he has been feeling ever since Gertrude married Claudius. He is angry, disgusted, insulted, confused, and frustrated because his mother has proven herself to be a weak woman and has connected herself inextricably to the man who (he is nearly certain) killed his father.
By the end of the scene, Hamlet relents a bit, it seems, because he does tell her the truth:
That I essentially am not in madness,
But mad in craft.
In the end, he must feel as if she has redeemed herself, for he does trust her with this great truth and asks her not to tell Claudius. She promises not to do so, and the test of her loyalty will be what she says when she next sees Claudius.
As Hamlet leaves the room (dragging Polonius's body with him), he does seem to have spent his anger and wishes her a good night.