Antonio cautions his brother Leonato not to be so upset about what has happened to Hero. Leonato responds that the advice of those who are not suffering themselves means absolutely nothing to those who are. In a long speech, he rails against attempts to “patch grief with proverbs,” (5.1.17) and “charm ache with air and agony with words.” (5.1.26) Antonio calls this opinion childish, and advises him to get back at Don Pedro, Don John and Claudio instead. Leonato agrees, admitting he has come to believe his daughter was lied about.
Leonato’s outrage and complaining make him act childish, despite his years and gray beard. His fit here is a lot like Claudio’s in the second act: he rejects the words and offers of help made by other people, choosing to trust only his own feelings.
Don Pedro and Claudio arrive. When Leonato accuses them of murdering his daughter with their slander, a fight almost breaks out. Leonato hints at challenging Claudio to a duel. Antonio, who thinks that his niece Hero is really dead, steps in and tries to start a fight right then and there. Leonato calms Antonio down, and leads him away.
Leonato has to keep his brother from ruining the entire plan: Claudio will marry Hero after her name has been cleared.
Benedick arrives. Claudio and Don Pedro say that they had been looking for him, and mention the fight they almost had with the old men just before. When Claudio asks Benedick to cheer them up with his wit, he replies that it is in his scabbard—do they want him to draw? Benedick challenges Claudio to a duel, and Claudio accepts. Claudio implies that beating Benedick will be as easy as carving meat at a feast. Not yet believing that Benedick is serious about dueling, Don Pedro teases him about Beatrice’s love. Paying no attention to this, Benedick leaves, promising to meet “Lord Lackbeard,” (5.1.192) later in combat. As he goes, he mentions that Don John has fled from the city, suggesting that running away probably means he is guilty of something or other. Don Pedro and Claudio finally realize that Benedick is not kidding, concluding that he has lost his reason out of love for Beatrice.
To show that he isn’t joking around, Benedick implies that his sword is his wit. Earlier in the play, characters spoke about violence as a metaphor for battles of wit. Now, the reverse is true: Benedick and Claudio talk about witty banter and “carving meat,” for a feast, but really mean violence. Benedick uses Claudio’s lack of a beard to insult him and suggest that he is not masculine. It is ironic that Claudio accuses Benedick of losing his wits over love. After all, it’s Claudio’s passion for Hero that has caused the confused and dangerous situation in this scene.
Dogberry, Verges and the members of the watch arrive with Borachio and Conrade in their custody. Don Pedro is shocked to see two of his brother’s men arrested. Dogberry has Borachio confess his treachery, and Borachio brags that “I have deceived even your very eyes; what your wisdoms could not discover, these shallow fools have brought to light.” (5.1.231-233) Don Pedro and Claudio are filled with remorse for their awful mistake, and Claudio exclaims that he again loves Hero as he did when he first saw her.
Borachio reveals one of the central ironies of the play: the information needed to stop the evil plan has somehow ended up in the hands of the most incompetent characters. We can see this as a delaying tactic by Shakespeare. The long time it takes for the truth to come out allows for the story to unfold in more interesting ways.
Leonato and Antonio reenter, and Leonato forgives Claudio on the condition that he will admit Hero’s innocence, put an epitaph on her tomb, and marry Leonato's niece. Claudio, filled with gratitude and regret, agrees to do so. Though it is totally unrelated to the conversation going on (as well as inappropriate), Dogberry complains to Leonato that Conrade called him an ass, and urges Leonato to correct him. Leonato and the members of the watch head off to interrogate Margaret about her involvement in the scheme.
Leonato sends Claudio to a funeral right before the wedding. This is intended to heighten Claudio’s surprise and joy at finding Hero still alive in the final scene. Once again, it is a ploy or tactic in the "war" of love. Dogberry’s biggest problem in language is also his biggest problem in social situations. Just as he doesn’t know which word belongs in which sentence, he doesn’t know what kind of behavior is appropriate in a given situation.