Much Ado About Nothing is a comic version of Romeo and Juliet. It all goes well until the night before the wedding, to when Hero is thought to be unfaithful. After this, on the wedding day, the play carefully walks the tightrope between comedy and tragedy. It could go either way: Hero's father could kill her; Hero could kill herself; Benedick could kill Claudio; and Pedro could kill Benedick.
All goes well in tragedy and comedy until Act III. In Romeo and Juliet, all goes well until Romeo is banished. Then, Juliet must fake her death in order for the two lovers to be reunited. Well, in Much Ado, Hero is likewise exiled in Act III. Instead of swordfighting in the street, Hero is simply accused of not being a virgin. This is the tragic and sexist double standard that could so easily throw comedy into tragedy. Men are banished through blood; women are banished through rumor.
Luckily, tragedy is averted by Beatrice, a kind of Friar Lawrence intercessory. It takes all of Beatrice's powers to convince Benedict to defend a "whore." This goes against his life's training: Benedict has been taught to distrust women, namely unfaithful ones. Love doesn't change him: a feminist does.
Benedict's challenge of Claudio could very well lead to tragedy, but, luckily, the comedy ends as a comedy should: by accident. A buffoon uncovers Don John's plot. Borachio confesses. Claudio and Pedro hold vigil. Claudio weds Hero's sister instead. Don John is captured. Instead of one funeral, we have a fake funeral and two weddings.
Instead of the swords of tragedy, Much Ado uses the words that could lead to both.