In Shakespeare's Hamlet, the young prince discovers that his sire, Old Hamlet (the deceased King of Denmark) has been murdered.
On the battlements in Act One, the Ghost walks repeatedly, looking much like the old king. Hamlet is informed and goes to speak to the spirit that night. It is indeed his father's ghost, and he tells Hamlet that Claudius (Old Hamlet's brother) murdered him with poison poured into his ear while he took his daily nap in the orchard.
In Elizabethan society, it was deemed a mortal sin to kill a king. This meant that to do so, one would forfeit his or her immortal soul. So although Old Hamlet asks Hamlet to avenge his death, Hamlet hesitates. He's not certain that the ghost is an "honest" one. If the devil wants to trick Hamlet into losing his soul, he might send a ghost to trick Hamlet into committing a mortal sin. So Hamlet goes about looking for proof that Claudius killed Old Hamlet.
Hamlet arranges to have a group of traveling players put on a performance that reenacts Old Hamlet's murder. He believes that when Claudius sees the performance, if he is guilty he will be unable to hide his surprise and culpability, and Hamlet will have his proof.
Not only has Claudius killed his brother, but he also quickly married Gertrude, the old king's wife and Hamlet's mother. While Hamlet has no reason to believe that Gertrude was involved in her husband's death, he is scornful of the speed with which she seemed to forget her dead husband only to marry his brother.
In Act One, scene two, Gertrude asks Hamlet to stop acting so depressed over his father's death. Death, she notes, is a natural part of life. He agrees. She points out that if he does agree, why does he seem so devastated. His response not only describes how he feels, but draws a strong contrast between his depth of response and his mother's seeming lack of response: for he asserts that with him it is not a question of what "seems" or "appears" to be—which can be faked. For Hamlet, his mourning is sincere—it's about how he truly feels.
Seems, madam? Nay, it is. I know not seems. (79)
When Hamlet arranges for the phony play, he includes verbiage that will reflect his mother's devoted behavior to his father, to draw an obvious comparison between how she was before her husband died and her ability to marry another man so soon after his death.
The Player Queen vows her endless devotion to her husband. She also promises that she would never marry again for her love is too enduring to get over. If she marries again, she hopes she will be cursed.
O, confound the rest!
Such love must needs be treason in my breast.
In second husband let me be accurst! (III.ii.67-69)
The Player Queen continues, saying once more that if she is widowed, she will turn her back on anything that is pleasurable. If she does not, she hopes to suffer abiding pain.
Meet what I would have well, and it destroy,
Both here and hence pursue me lasting strife,
If, once a widow, ever I be wife! (211-213)
When Hamlet asks his mother how she likes the play so far, Gertrude says:
The lady doth protest too much, methinks. (III.ii.221)
Gertrude's response can be taken two ways. In saying that the Player Queen protests too much, she may be thinking that the actor's portrayal is unrealistic in that player queen keeps going on and on. Gertrude may not be thinking about her relationship with Old Hamlet because in scene four, when Hamlet begins to yell as his mother, she asks him what she has done to deserve such treatment. One might think that she is not very smart to miss the connection between the players' presentation and its similarity to her own situation. However, we get the sense from Hamlet, as he recalls his father's desire to protect Gertrude even from a harsh wind, that she may not have had a great deal to do with affairs of state and/or the more serious side of being a queen. It is entirely possible that she married Claudius because she was fearful of what kind of position she would have in the world as a widow when Claudius became king and not Hamlet.
The other possibility is that Gertrude does recognize the truth in the players' drama and is humiliated and filled with self-loathing because she knows full well that she made those promises and did not keep them. In this case the intent of her comment would have been to make light of something that was too terrible to face. Her wish not to face the dark side of her heart is something she speaks about with Hamlet in scene four:
O Hamlet, speak no more!
Thou turn'st mine eyes into my very soul,
And there I see such black and grained spots
As will not leave their tinct. (III.iv.95-98)
The play within the play in 3.2 is directed at two individuals. The first scene with the player queen is directed at Gertrude. This is called "The Mousetrap". Gertrude is the mouse. (See Act 3 Scene 4, in Gertrude's closet.) The next scene referenced as "The Murder of Gonzago" is designed to catch Claudius. It is a mistake to conclude that the whole play within the play is directed at Claudius alone.
The player queen in her speech belabors the player king's invitation for the player queen to remarry after he dies. The player queen abhors the idea. She declares as a matter of fact that marrying a second husband necessarily involved the murder of the first. The question isn't whether Gertrude killed her husband but whether she was aware of Claudius' plot. Being completely guiltless about Claudius' deed, the player queen's protest about remarriage makes no sense to Gertrude. Gertrude thinks the player queen's fears and her protest are pointless exaggeration. The more telling comment though comes from Claudius who does see some accusation in the player queen's protest. Hamlet almost gives away the farm by mentioning "poison" but that is another discussion.