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.

Elsewhere, Dogberry, Verges, and the Watch interrogate Borachio and Conrad. Borachio confesses that he received money from Don John for pretending to make love to Hero and then lying about it to Claudio and Don Pedro. When they hear about what has happened at the wedding, the watchmen tie up the captives and take them to Leonato’s house.

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” (IV.i.30–31).

Although the usually quiet Hero speaks up in her own defense, Claudio does not allow her even the possibility of defending herself. When she blushes in shock and humiliation, he cries:

Hero’s reactions of horror become, in Claudio’s description of her face, evidence of her guilt, making it impossible for her to offer any defense. Claudio similarly discards Hero’s denial of the accusation when she says, “I talked with no man at that hour, my lord” (IV.i.85). Claudio is convinced—by his eyes, by his own suspicious nature, and by his certainty that he cannot have been mistaken—that he knows the truth. He has already tried and convicted Hero in his mind, and she is afforded no chance to prove her virtue.

Following immediately upon these moments of betrayal and pain, however, seeds are sown for resolution and redemption. The trick that the friar plans is ingenious, and it seems to be a good one. It also plays cunningly upon a simple fact of human nature:

As soon as Hero’s accusers think her dead, the friar realizes, much of the anger driving Claudio and the others will dissipate, and they will start to remember her good qualities and regret their poor treatment of her. The “greater birth” that the friar envisions will transform Hero from an object of scorn and slander into someone mourned and better beloved than when she was alive (IV.i.212). In order to wash away her alleged sin, then, Hero will have to die and be symbolically reborn.

The scene also marks a critical turning point in the relationship between Benedick and Beatrice. Benedick seems to make an important decision when he stays behind in the church with Beatrice and her family instead of leaving with Claudio, Don Pedro, and Don John. His loyalty, which lies with his soldier friends when he arrives in Messina, now draws him to stay with Beatrice. In their elliptical ways, Beatrice and Benedick confess their love to one another after everyone else has left the church. Beatrice’s confused answer to Benedick’s blurting out that he loves her reveals that she is hiding something. Indeed, when Benedick exultantly exclaims that she loves him, she finally admits it: “I love you with so much of my heart that none is left to protest” (IV.i.284–285).

Lost in his newfound love, Benedick apparently converts himself to Beatrice’s way of thinking. Soberly he asks her whether she truly believes that Claudio has slandered Hero. When Beatrice answers yes, Benedick says, “Enough, I am engaged, I will challenge him. I will kiss your hand, and so I leave you” (IV.i.325–326). Spurred by his own conscience, his love for Beatrice, and his trust in Beatrice’s judgment, Benedick makes the radical decision to challenge Claudio to a duel to the death for what he has done to Hero. The lines of loyalty in the play have changed considerably.