Who are the characters in Act 1 of Shakespeare's Much Ado About Nothing? What happens in the first act?

Shakespeare's comedy Much Ado About Nothing takes place in five acts. In Act I, Scene 1, Leonato–together with his daughter Hero and his niece Beatrice–prepares to welcome Don Pedro and his soldiers home from the war and host them in his home in Messina. Leonato learns from a messenger that Don Pedro favors a young soldier named Claudio, who has proven himself on the battlefront. Beatrice inquires after another soldier–Benedick. The Messenger speaks well of Benedick as a soldier, but Beatrice responds sarcastically, disparaging Benedick's character. Leonato reveals that Beatrice and Benedick are engaged in an ongoing battle of wits.

Don Pedro arrives, accompanied by Claudio, Benedick, Don John, and Balthasar. As greetings are exchanged, Benedick and Beatrice immediately start verbally sparring. Don Pedro introduces his traitorous brother Don John, who–although back in Don Pedro's good graces–is essentially a prisoner.

In private, Claudio asks Benedick his opinion of their hostess Hero: Benedick's response indicates he thinks little of marriage, though that is clearly what Claudio has in mind. Don Pedro agrees to help Claudio woo Hero by masquerading as Claudio at a dance that night and declaring his intentions to Hero and–if all goes well–her father Leonato.

In Act I, Scene 2, Antonio relays to his brother Leonato that one of his men overheard Don Pedro and Claudio discussing Hero. Antonio's man misunderstood the conversation, however, as he says Don Pedro plans to ask for Hero's hand that night.

In Act I, Scene 3, Conrade tries to cheer up Don John, who freely admits his villainous nature. Borachio arrives with the news that Claudio intends to propose to Hero. Don John seizes upon the news and begins to plan mischief. And so the stage is set...