With the wedding scene—the climax of the play—the tone takes an abrupt turn, plunging from high comedy into tragedy. Claudio’s rejection of Hero is designed to inflict as much pain as possible, and Hero’s and Leonato’s reactions to it seem to make things even worse. Few accusations could cause a woman more harm in the Renaissance than that of being unchaste, and Claudio uses deliberately theatrical language to hurt Hero publicly, in front of friends and family. The rejection scene also throws other relationships in the play into question: Claudio and Don Pedro both suggest that it reflects badly on Leonato’s social manners to have tried to foist off a woman like Hero on Claudio, and Don Pedro implies that his own reputation has suffered by way of the apparent discovery that he and Claudio have made regarding Hero’s virginity. Claudio assaults Leonato by denigrating Hero: “Give not this rotten orange to your friend. / She’s but the sign and semblance of her honour”.
Everyone gathers inside the church to celebrate the wedding of Claudio and Hero. But when Friar Francis asks Claudio whether he wishes to marry Hero, Claudio breaks into an outraged speech. He tells Leonato that he sends Hero back to Leonato again, for though she seems outwardly pure and blushes with innocence, her outward features belie her inward corruption and that she is, in fact, an unchaste, unfaithful whore. The happy wedding transforms itself into a chaotic uproar. Leonato and the shaken Hero ask what Claudio means. Claudio tells Leonato, in front of everyone in the church, that the night before Claudio, Don Pedro, and Don John watched Hero “tal[k]” with a vile man at her window (IV.i.82). This man has also “[c]onfessed” to having had sexual encounters with Hero many times before (IV.i.92). Don Pedro supports Claudio’s accusations, and they, together with Don John, accuse Hero of sexual looseness. Leonato cries out in despair, asking for a dagger with which to commit suicide. The overwhelmed Hero sinks to the ground, unconscious. Benedick and Beatrice rush to offer her their assistance, while Claudio, Don Pedro, and Don John leave the church without looking back. Leonato, weeping, tells Benedick and Beatrice to let Hero die, since that would be better than for her to live in shame. Beatrice, however, remains absolutely convinced that her cousin has been slandered.
Suddenly and unexpectedly, the friar steps in. A quiet observer to the whole proceeding, he has wisely determined from the expressions of shock he has seen on Hero’s face that she is not guilty of unfaithfulness. Hero regains consciousness and insists that she is a virgin, that she has been entirely faithful to Claudio, and that she has no idea what her accusers are talking about. The intelligent Benedick realizes that if the accusation is a lie, it must originate with the troublemaking Don John, who would happily trick these two to spoil their happiness.
The friar comes up with an unexpected plan: he suggests that Hero’s existence be concealed, and that Leonato tell everyone she has died of shock and grief. When her accusers hear that an innocent woman has died, their anger will turn into regret, and they will start to remember what a virtuous lady Hero was. If the accusation really is a trick, then perhaps the treachery will expose itself, and Hero can return to the world. In the worst-case scenario, Hero can later be taken off quietly and placed in a convent to become a nun. The grieving, confused Leonato agrees to go along with the plan.
The others depart with Hero, leaving Benedick and Beatrice alone together. Benedick, trying to comfort Beatrice, asks if there is any way he can show his friendship to her. He suddenly confesses that he is in love with her, acknowledging how strange it is for his affections to reverse so suddenly, and she, equally startled and confused, replies in similar terms. But when Benedick says that he will do anything for Beatrice, she asks him to kill his friend Claudio. The shocked Benedick refuses. Angry, Beatrice denounces Claudio’s savagery, saying that if she were a man she would kill him herself for his slander of her cousin and the cruelty of his trick. After listening to her, Benedick changes his mind and soberly agrees to challenge Claudio—for the wrong that he has done to Hero and for Beatrice’s sake.