Elsewhere, Don Pedro, Claudio, and Leonato begin to tease Benedick about his decision never to marry. Benedick announces that he has changed, and the others agree; they have noticed that he is much quieter. They say that he must be in love and tease him about it. But Benedick is too subdued even to answer their jokes. He takes Leonato aside to speak with him.
As soon as Claudio and Don Pedro are left alone, Don John approaches them. He tells them that he is trying to protect Don Pedro’s reputation and save Claudio from a bad marriage. Hero is a whore, he says, and Claudio should not marry her. The two are shocked, of course, but Don John immediately offers them proof: he tells them to come with him that night to watch outside Hero’s window where they will see her making love to somebody else. Claudio, already suspicious and paranoid, resolves that if what he sees tonight does indeed prove Hero’s unfaithfulness, he will disgrace her publicly during the wedding ceremony the next day, and Don Pedro vows to assist him. Confused, suspicious, and full of dark thoughts, Claudio and Don Pedro leave with Don John.