Don Pedro, prince of Aragon, is visiting Messina after a victorious military engagement elsewhere. With him are his half-brother Don John, with whom he has quarreled and recently reconciled, and his friends and fellow soldiers, Claudio and Benedick. The company of soldiers is greeted warmly by Leonato, governor of Messina—and his charming daughter Hero and witty niece Beatrice, both of marriageable age. Benedick and Beatrice immediately resume a long-standing “merry war” of words; but Claudio and Hero and smitten by love-at-first-sight and are betrothed at a masked ball, mainly through the efforts of Don Pedro.
As this wedding is being planned, Don Pedro, Leonato, and Claudio also vow to make husband and wife of Benedick and Beatrice, both professed enemies of marriage. The three friends stage a conversation for Benedick’s benefit in which they pretend concern over Beatrice’s imagined passion for Benedick. They see no happiness for her in such a love, since her pride will not allow her to confess her affection and Benedick’s price will not allow him to accept it. They sadly (and humorously) conclude that Beatrice should conquer her passion as best she can. Benedick, who is eavesdropping on their conversation, is completely taken in by the ruse. He resolves that, if Beatrice loves him, her love shall be requited. In another part of the estate, Hero and her attendant, Ursula, put on a similar charade for Beatrice, who is eavesdropping on their conversation. Beatrice, like Benedick, is chastened at this revelation of how she appears to others and vows to return Benedick’s love.
In the meantime the villainous Don John, still angry at his brother and jealous of Claudio, joins with his henchmen, Borachio and Conrade, and plots to prevent the marriage of Claudio and Hero. They trick the young suitor into thinking Hero has another lover by having her servant, Margaret, dress in Hero’s clothes and talk to Borachio at her chamber window the night before the wedding. Borachio calls Margaret by Hero’s name, and Claudio, incredulous and angry, overhears.
Later, a drunken Borachio cannot resist boasting of this adventure and is overheard by the night watchmen. Although the watchmen imperfectly understand the full meaning of the conversation, they recognize Borachio as a villain, arrest him and Conrade, and turn them over to country constable, Dogberry, and simple headborough, Verges.
The next day at the church, Claudio accuses Hero of being unchaste and refuses to marry her. She falls down in a faint, and Don Pedro, Don John, and Claudio leave hastily. Beatrice and the friar who was to have performed the ceremony are certain of Hero’s innocence, while Leonato and Benedick know not what to think. The friar advises an inflamed Leonato to publicly report that Hero has died of shame; and Benedick, touched by Beatrice’s distress, confesses his love for her, as does Beatrice for him. However, Beatrice asks Benedick to prove his love by killing Claudio. Torn between loyalty to his friend and to his new love, he reluctantly agrees to challenge Claudio.
In the meantime, Dogberry, Verges, and the watchmen have successfully interrogated their prisoners and extracted a confession. When Claudio learns of the treachery, he promises he will do anything to make amends, and Leonato secures his promise to marry an unknown cousin of Hero’s.
The next morning, a disguised Hero is presented to Claudio as her cousin; but, when he takes her hand, she removes her mask and explains that she had only died while her name was dishonored. Claudio is delighted to learn his love still lives, and the bride is very much eager to continue her interrupted wedding. In addition, Beatrice and Benedick now publicly profess their love for one another and are determined to marry, even after learning their romance was spurred on by a trick.
The resulting double wedding of Hero and Claudio and Beatrice and Benedick is followed by an announcement that Don John’s attempt to flee has been unsuccessful, and he has been arrested. On that happy note the play ends, and all tribulations are now regarded as much ado about nothing.