The people of Vienna are running wild.
According to Booker, in this stage, "we see a little world in which people have passed under a shadow of confusion, uncertainty, and frustration, and are cut off from one another." Vienna is a world in which the people have thumbed their noses at the law – the (illegal) sex industry is out of control, STDs are rampant, and the numbers of illegitimate children are on the rise.
Angelo's "vengeful hypocrisy" makes everyone miserable.
Booker says that in this phase, the "pressure of darkness" puts everyone in a "nightmarish tangle." Angelo has sentenced Claudio to death for the crime of "fornication" and places Isabella in the worst possible position – she can have sex with Angelo to save her brother's life or, she can refuse and watch her brother die.
Angelo is forced to recognize his own darkness.
When the Duke shows up and confronts Angelo, this "dark figure" is forced to recognize that he is a "monster of vengeful hypocrisy." Angelo is contrite so the Duke can offer him a pardon. This, according to Booker, is what paves the way for every other character's "happiness" (i.e., marriage). We'd like to point out, however, that, even though four couples are set to get married at the play's end, not everyone is "happy." Check out "What's Up With the Ending?" for more on this.