Act III of Shakespeare's poetic tragedy Romeo and Juliet illustrates the young lovers' impetuousity and adolescent moodiness which effect the complication of the plot and further the sense of foreboding, a feeling Friar Laurence has earlier sensed in his observation, "These violent delights have violent ends" (2.6.9).
As mercurial as his slain friend, Romeo becomes insensed when Tybalt kills Mercutio; in his impulsive anger, Romeo slays Tybalt, then hysterically cries, "O, I am Fortune's fool!" (3.1.136) Continuing in his rashness, Romeo flees to the sanctuary of Friar Lautence's cell, flings himself upon the floor and cries:
There is no world without Verona walls,Like Romeo, Juliet reacts with exaggerated emotion and despair, capriciously wavering between hatred for Tybalt to hatred for Romeo:What storm is this that blows so contrary? Is Romeo slaught'red, and is Tybalt dead? My dear-lov'd cousin, and my dearer lord? Then, dreadful trumpet, sound the general doom!(70) For who is living, if those two are gone?
But purgatory, torture, hell itself.
Hence banished is banish'd from the world,
And world's exile is death. Then ‘banishment’
Is death misterm'd. Calling death ‘banishment,’
Thou cut'st my head off with a golden axe
And smilest upon the stroke that murders me. (3.3.18-24)
With the turbulent emotions of Romeo and Juliet there is the complication of the plot as the enmity between the Montague and Capulet families waxes, as well as the terrible presentiment of the future for the young lovers. As Juliet foretells, the "general doom" is, indeed, sounded.
In Romeo and Juliet, by William Shakespeare, the things that most dramatically change the mood of the play are:
Tybalt picks a fight with Mercutio and while Romeo tries to break up the fight, Tybalt slips under Romeo's arm and kills Mercutio. Romeo has done everything he possible to placate Tybalt, refusing to fight with him (as they are now related). However, once Mercutio dies, Romeo goes looking for Tybalt, and when they fight, Romeo kills the other man.
So Romeo is first guilty of killing a member of the enemy family of the Capulets. But he is also guilty of killing one of his wife's family members. And this is something Juliet will for a short time struggle with.
However, when the incident comes before Prince Escalus, he does not order Romeo's death, under the circumstances, but he banishes Romeo, who may never return to Verona again. Romeo believes that he might as well be dead—as being separated from Juliet means death.
Ha! Banishment! Be merciful, say 'death'. / For exile hate more terror in his look, / Much more than death. Do not say banishment. (III, iii, 13-15)
Romeo and Juliet have their one night of wedded bliss; too soon, Romeo must leave or be killed for still residing in Verona.
If all of this is not enough, Juliet's parents insist that Juliet marry Paris within the week, and threaten to disown her if she does not. Then the Nurse tells Juliet to forget Romeo and marry Paris, even though Juliet is already married. At this point, Juliet turns her back on the Nurse, no longer confiding in her.
It is during Act III that things begin to unravel. It will be because of these occurrences and circumstances that Juliet will take steps to avoid marriage to Paris, and the misadventures of our star-crossed lovers will lead to their tragic end.